diff --git a/DDG4/lcio/Geant4Output2LCIO.cpp b/DDG4/lcio/Geant4Output2LCIO.cpp
index d5adee47045faa3436e6f9da5fed22c26c08bc4c..2aa8ff6ded5a733769886ecf6bd34aab50425f84 100644
--- a/DDG4/lcio/Geant4Output2LCIO.cpp
+++ b/DDG4/lcio/Geant4Output2LCIO.cpp
@@ -183,17 +183,17 @@ lcio::LCCollectionVec* Geant4Output2LCIO::saveParticles(Geant4ParticleMap* parti
       MCParticleImpl* q = new lcio::MCParticleImpl();
       q->setPDG(p->pdgID);
 
-      float ps_fa[3] = {float(p->psx/GeV),float(p->psy/GeV),float(p->psz/GeV)};
+      float ps_fa[3] = {float(p->psx/CLHEP::GeV),float(p->psy/CLHEP::GeV),float(p->psz/CLHEP::GeV)};
       q->setMomentum( ps_fa );
 
-      double vs_fa[3] = { p->vsx/mm, p->vsy/mm, p->vsz/mm } ;
+      double vs_fa[3] = { p->vsx/CLHEP::mm, p->vsy/CLHEP::mm, p->vsz/CLHEP::mm } ;
       q->setVertex( vs_fa );
 
-      double ve_fa[3] = { p->vex/mm, p->vey/mm, p->vez/mm } ;
+      double ve_fa[3] = { p->vex/CLHEP::mm, p->vey/CLHEP::mm, p->vez/CLHEP::mm } ;
       q->setEndpoint( ve_fa );
 
-      q->setTime(p->time/ns);
-      q->setMass(p->mass/GeV);
+      q->setTime(p->time/CLHEP::ns);
+      q->setMass(p->mass/CLHEP::GeV);
       q->setCharge(def ? def->GetPDGCharge() : 0); // Charge(e+) = 1 !
 
       // Set generator status
diff --git a/DDG4/lcio/LCIOEventReader.cpp b/DDG4/lcio/LCIOEventReader.cpp
index 1a0cf097b1c039882db48f84ee4adfe3748972b0..5bda98d11ec22d5971a62b790a5c48d1d6b7da57 100644
--- a/DDG4/lcio/LCIOEventReader.cpp
+++ b/DDG4/lcio/LCIOEventReader.cpp
@@ -95,24 +95,24 @@ LCIOEventReader::readParticles(int event_number, vector<Particle*>& particles)
     PropertyMask status(p->status);
     p->pdgID        = pdg;
     p->charge       = int(mcp->getCharge()*3.0);
-    p->psx          = mom[0]*GeV;
-    p->psy          = mom[1]*GeV;
-    p->psz          = mom[2]*GeV;
-    p->time         = mcp->getTime()*ns;
-    p->properTime   = mcp->getTime()*ns;
-    p->vsx          = vsx[0]*mm;
-    p->vsy          = vsx[1]*mm;
-    p->vsz          = vsx[2]*mm;
-    p->vex          = vex[0]*mm;
-    p->vey          = vex[1]*mm;
-    p->vez          = vex[2]*mm;
+    p->psx          = mom[0]*CLHEP::GeV;
+    p->psy          = mom[1]*CLHEP::GeV;
+    p->psz          = mom[2]*CLHEP::GeV;
+    p->time         = mcp->getTime()*CLHEP::ns;
+    p->properTime   = mcp->getTime()*CLHEP::ns;
+    p->vsx          = vsx[0]*CLHEP::mm;
+    p->vsy          = vsx[1]*CLHEP::mm;
+    p->vsz          = vsx[2]*CLHEP::mm;
+    p->vex          = vex[0]*CLHEP::mm;
+    p->vey          = vex[1]*CLHEP::mm;
+    p->vez          = vex[2]*CLHEP::mm;
     p->process      = 0;
     p->spin[0]      = spin[0];
     p->spin[1]      = spin[1];
     p->spin[2]      = spin[2];
     p->colorFlow[0] = color[0];
     p->colorFlow[0] = color[1];
-    p->mass         = mcp->getMass()*GeV;
+    p->mass         = mcp->getMass()*CLHEP::GeV;
     const EVENT::MCParticleVec &par = mcp->getParents(), &dau=mcp->getDaughters();
     for(int num=dau.size(),k=0; k<num; ++k)
       p->daughters.insert(GET_ENTRY(mcparts,dau[k]));
diff --git a/DDG4/plugins/Geant4FieldTrackingSetup.cpp b/DDG4/plugins/Geant4FieldTrackingSetup.cpp
index a373565cb665a3a06dc4c3563d099563b47e73b7..6d89b84fedca72a8ab768ff3a474e82c3777ae06 100644
--- a/DDG4/plugins/Geant4FieldTrackingSetup.cpp
+++ b/DDG4/plugins/Geant4FieldTrackingSetup.cpp
@@ -141,7 +141,7 @@ namespace {
 Geant4FieldTrackingSetup::Geant4FieldTrackingSetup() : eq_typ(), stepper_typ() {
   eps_min            = -1.0;
   eps_max            = -1.0;
-  min_chord_step     =  1.0e-2 *mm;
+  min_chord_step     =  1.0e-2 *CLHEP::mm;
   delta_chord        = -1.0;
   delta_one_step     = -1.0;
   delta_intersection = -1.0;
diff --git a/DDG4/plugins/Geant4SDActions.cpp b/DDG4/plugins/Geant4SDActions.cpp
index f309cb56689a7509ebb6cc7a933e52a17415ca24..5b66094fa9d3e3d9b2c20fe8f138d30f50d5e62a 100644
--- a/DDG4/plugins/Geant4SDActions.cpp
+++ b/DDG4/plugins/Geant4SDActions.cpp
@@ -248,8 +248,8 @@ namespace DD4hep {
         collection->add(hit);
         sensitive->printM2("+++ TrackID:%6d [%s] CREATE hit combination with %2d deposit(s):"
                            " %e MeV  Pos:%8.2f %8.2f %8.2f",
-                           pre.truth.trackID,sensitive->c_name(),combined,pre.truth.deposit/MeV,
-                           pos.X()/mm,pos.Y()/mm,pos.Z()/mm);
+                           pre.truth.trackID,sensitive->c_name(),combined,pre.truth.deposit/CLHEP::MeV,
+                           pos.X()/CLHEP::mm,pos.Y()/CLHEP::mm,pos.Z()/CLHEP::mm);
         clear();
       }
 
@@ -265,7 +265,7 @@ namespace DD4hep {
           extractHit(coll);
         }
         /// There must be something in.
-        if ( h.deposit()/keV <= 0 )  {
+        if ( h.deposit()/CLHEP::keV <= 0 )  {
           return false;
         }
         /// Initialize the deposits of the next hit.
diff --git a/DDG4/src/Geant4Converter.cpp b/DDG4/src/Geant4Converter.cpp
index ba905b05920a7f713341e6ffb9f7b266ec99fa17..bd834e28da3dd2ff9c2b97f5bcb1a235445cafa5 100644
--- a/DDG4/src/Geant4Converter.cpp
+++ b/DDG4/src/Geant4Converter.cpp
@@ -294,7 +294,7 @@ void* Geant4Converter::handleElement(const string& name, const Atom element) con
         }
       }
       else {
-        g4e = new G4Element(element->GetTitle(), name, element->Z(), element->A() * (g / mole));
+        g4e = new G4Element(element->GetTitle(), name, element->Z(), element->A() * (CLHEP::g / CLHEP::mole));
       }
       stringstream str;
       str << (*g4e);
@@ -313,7 +313,7 @@ void* Geant4Converter::handleMaterial(const string& name, Material medium) const
     if (!mat) {
       TGeoMaterial* m = medium->GetMaterial();
       G4State state = kStateUndefined;
-      double density = m->GetDensity() * (gram / cm3);
+      double density = m->GetDensity() * (CLHEP::gram / CLHEP::cm3);
       if (density < 1e-25)
         density = 1e-25;
       switch (m->GetState()) {
diff --git a/DDG4/src/Geant4InputHandling.cpp b/DDG4/src/Geant4InputHandling.cpp
index fb34c11eeecea1a15c368e22e19aa8ffbeffbb09..2adb54e2222aef555ee72086d8da60ffb14bd64b 100644
--- a/DDG4/src/Geant4InputHandling.cpp
+++ b/DDG4/src/Geant4InputHandling.cpp
@@ -156,8 +156,8 @@ int DD4hep::Simulation::boostInteraction(const Geant4Action* /* caller */,
     // Now move begin and end-vertex of all primary vertices accordingly
     for(iv=inter->vertices.begin(); iv != inter->vertices.end(); ++iv)  {
       Geant4Vertex* v = (*iv).second;
-      double t = gamma * v->time + betagamma * v->x / c_light;
-      double x = gamma * v->x + betagamma * c_light * v->time;
+      double t = gamma * v->time + betagamma * v->x / CLHEP::c_light;
+      double x = gamma * v->x + betagamma * CLHEP::c_light * v->time;
       double y = v->y;
       double z = v->z;
       v->x = x;
@@ -169,8 +169,8 @@ int DD4hep::Simulation::boostInteraction(const Geant4Action* /* caller */,
     // Now move begin and end-vertex of all primary and generator particles accordingly
     for(ip=inter->particles.begin(); ip != inter->particles.end(); ++ip)  {
       Geant4ParticleHandle p = (*ip).second;
-      double t = gamma * p->time + betagamma * p->vsx / c_light;
-      double x = gamma * p->vsx + betagamma * c_light * p->time;
+      double t = gamma * p->time + betagamma * p->vsx / CLHEP::c_light;
+      double x = gamma * p->vsx + betagamma * CLHEP::c_light * p->time;
       double y = p->vsx;
       double z = p->vsz;
 
@@ -318,7 +318,7 @@ int DD4hep::Simulation::generatePrimaries(const Geant4Action* caller,
     G4PrimaryVertex* v4 = new G4PrimaryVertex(v->x,v->y,v->z,v->time);
     event->AddPrimaryVertex(v4);
     caller->print("+++++ G4PrimaryVertex at (%+.2e,%+.2e,%+.2e) [mm] %+.2e [ns]",
-                  v->x/mm,v->y/mm,v->z/mm,v->time/ns);
+                  v->x/CLHEP::mm,v->y/CLHEP::mm,v->z/CLHEP::mm,v->time/CLHEP::ns);
     for(Geant4Vertex::Particles::const_iterator ip=v->out.begin(); ip!=v->out.end(); ++ip)  {
       Geant4ParticleHandle p = pm[*ip];
       if ( p->daughters.size() > 0 )  {
diff --git a/DDG4/src/Geant4IsotropeGenerator.cpp b/DDG4/src/Geant4IsotropeGenerator.cpp
index b0b83b06e7866c77920766ae83857c5b8bfd07b0..c0ea420f382d1c628e603617f845c66f57db028c 100644
--- a/DDG4/src/Geant4IsotropeGenerator.cpp
+++ b/DDG4/src/Geant4IsotropeGenerator.cpp
@@ -33,7 +33,7 @@ Geant4IsotropeGenerator::Geant4IsotropeGenerator(Geant4Context* context, const s
   InstanceCount::increment(this);
   m_needsControl = true;
   declareProperty("Particle",      m_particleName = "e-");
-  declareProperty("Energy",        m_energy = 50 * MeV);
+  declareProperty("Energy",        m_energy = 50 * CLHEP::MeV);
   declareProperty("Multiplicity",  m_multiplicity = 1);
   declareProperty("Mask",          m_mask = 0);
   declareProperty("Position",      m_position);
@@ -94,7 +94,7 @@ void Geant4IsotropeGenerator::operator()(G4Event*) {
     inter->particles.insert(make_pair(p->id,p));
     vtx->out.insert(p->id);
     printout(INFO,name(),"Particle [%d] %s %.3f GeV direction:(%6.3f %6.3f %6.3f)",
-             p->id, m_particleName.c_str(), momentum/GeV, x1, x2, x3);
+             p->id, m_particleName.c_str(), momentum/CLHEP::GeV, x1, x2, x3);
 
   }
 }
diff --git a/DDG4/src/Geant4Particle.cpp b/DDG4/src/Geant4Particle.cpp
index b9c7a7dda7dbcd469c6fbf082f7d26a27383ba00..581333e7ec636dbb22afc9c18d58d66bf7fb2f64 100644
--- a/DDG4/src/Geant4Particle.cpp
+++ b/DDG4/src/Geant4Particle.cpp
@@ -283,7 +283,7 @@ void Geant4ParticleHandle::dumpWithVertex(int level, const std::string& src, con
            "+++ %s ID:%3d %-12s status:%08X PDG:%6d Vtx:(%+.2e,%+.2e,%+.2e)[mm] "
            "time: %+.2e [ns] #Dau:%3d #Par:%1d%-6s",
            tag,p->id,p.particleName().c_str(),p->status,p->pdgID,
-           p->vsx/mm,p->vsy/mm,p->vsz/mm,p->time/ns,
+           p->vsx/CLHEP::mm,p->vsy/CLHEP::mm,p->vsz/CLHEP::mm,p->time/CLHEP::ns,
            p->daughters.size(),
            p->parents.size(),
            text);
@@ -306,7 +306,7 @@ void Geant4ParticleHandle::dumpWithMomentum(int level, const std::string& src, c
            "+++%s ID:%3d %-12s stat:%08X PDG:%6d Mom:(%+.2e,%+.2e,%+.2e)[MeV] "
            "time: %+.2e [ns] #Dau:%3d #Par:%1d%-6s",
            tag,p->id,p.particleName().c_str(),p->status,p->pdgID,
-           p->psx/MeV,p->psy/MeV,p->psz/MeV,p->time/ns,
+           p->psx/CLHEP::MeV,p->psy/CLHEP::MeV,p->psz/CLHEP::MeV,p->time/CLHEP::ns,
            int(p->daughters.size()),
            int(p->parents.size()),
            text);
@@ -328,8 +328,8 @@ void Geant4ParticleHandle::dumpWithMomentumAndVertex(int level, const std::strin
            "+++%s %3d %-12s stat:%08X PDG:%6d Mom:(%+.2e,%+.2e,%+.2e)[MeV] "
            "Vtx:(%+.2e,%+.2e,%+.2e)[mm] #Dau:%3d #Par:%1d%-6s",
            tag,p->id,p.particleName().c_str(),p->status,p->pdgID,
-           p->psx/MeV,p->psy/MeV,p->psz/MeV,
-           p->vsx/mm,p->vsy/mm,p->vsz/mm,
+           p->psx/CLHEP::MeV,p->psy/CLHEP::MeV,p->psz/CLHEP::MeV,
+           p->vsx/CLHEP::mm,p->vsy/CLHEP::mm,p->vsz/CLHEP::mm,
            int(p->daughters.size()),
            int(p->parents.size()),
            text);
diff --git a/DDG4/src/Geant4ParticleGun.cpp b/DDG4/src/Geant4ParticleGun.cpp
index 7a0705a5f669f84069ef8213c058002f8114e401..8b873c69bc4e7848f5152c92673f917fe6a3a383 100644
--- a/DDG4/src/Geant4ParticleGun.cpp
+++ b/DDG4/src/Geant4ParticleGun.cpp
@@ -36,7 +36,7 @@ Geant4ParticleGun::Geant4ParticleGun(Geant4Context* context, const string& name)
   InstanceCount::increment(this);
   m_needsControl = true;
   declareProperty("particle", m_particleName = "e-");
-  declareProperty("energy", m_energy = 50 * MeV);
+  declareProperty("energy", m_energy = 50 * CLHEP::MeV);
   declareProperty("multiplicity", m_multiplicity = 1);
   declareProperty("position", m_position);
   declareProperty("direction", m_direction);
@@ -82,7 +82,7 @@ void Geant4ParticleGun::operator()(G4Event* event)   {
     }
   }
   print("Shoot [%d] %.3f GeV %s pos:(%.3f %.3f %.3f)[mm] dir:(%6.3f %6.3f %6.3f)",
-        m_shotNo, m_energy/GeV, m_particleName.c_str(),
+        m_shotNo, m_energy/CLHEP::GeV, m_particleName.c_str(),
         m_position.X(), m_position.Y(), m_position.Z(),
         m_direction.X(),m_direction.Y(), m_direction.Z());
 
diff --git a/DDG4/src/Geant4ParticleHandler.cpp b/DDG4/src/Geant4ParticleHandler.cpp
index 050a546f821c1658323ed65f74e15683d8d1cd5d..cc538c2babc95cc11ae183f2e91c846de31b3fc1 100644
--- a/DDG4/src/Geant4ParticleHandler.cpp
+++ b/DDG4/src/Geant4ParticleHandler.cpp
@@ -70,7 +70,7 @@ Geant4ParticleHandler::Geant4ParticleHandler(Geant4Context* context, const strin
   declareProperty("PrintStartTracking",  m_printStartTracking = false);
   declareProperty("KeepAllParticles",    m_keepAll = false);
   declareProperty("SaveProcesses",       m_processNames);
-  declareProperty("MinimalKineticEnergy",m_kinEnergyCut = 100e0*MeV);
+  declareProperty("MinimalKineticEnergy",m_kinEnergyCut = 100e0*CLHEP::MeV);
   m_needsControl = true;
 }