diff --git a/include/RMGHardware.hh b/include/RMGHardware.hh
index 01ddc406..8328e2f7 100644
--- a/include/RMGHardware.hh
+++ b/include/RMGHardware.hh
@@ -76,6 +76,7 @@ class RMGHardware : public G4VUserDetectorConstruction {
     /// List of GDML files to load
     std::vector<std::string> fGDMLFiles;
     bool fGDMLDisableOverlapCheck = false;
+    int fGDMLOverlapCheckNumPoints = 3000;
     /// Mapping between physical volume names and maximum (user) step size to apply
     std::map<std::string, double> fPhysVolStepLimits;
 
diff --git a/src/RMGHardware.cc b/src/RMGHardware.cc
index 82e7ed29..9aafbab5 100644
--- a/src/RMGHardware.cc
+++ b/src/RMGHardware.cc
@@ -20,6 +20,7 @@ namespace fs = std::filesystem;
 
 #include "G4GDMLParser.hh"
 #include "G4GenericMessenger.hh"
+#include "G4GeomTestVolume.hh"
 #include "G4LogicalVolume.hh"
 #include "G4PhysicalVolumeStore.hh"
 #include "G4SDManager.hh"
@@ -43,7 +44,7 @@ G4VPhysicalVolume* RMGHardware::Construct() {
   if (!fGDMLFiles.empty()) {
     RMGLog::Out(RMGLog::debug, "Setting up G4GDMLParser");
     G4GDMLParser parser;
-    parser.SetOverlapCheck(!fGDMLDisableOverlapCheck);
+    parser.SetOverlapCheck(false); // overlap check is performed below.
     for (const auto& file : fGDMLFiles) {
       RMGLog::Out(RMGLog::detail, "Reading ", file, " GDML file");
       if (!fs::exists(fs::path(file.data()))) RMGLog::Out(RMGLog::fatal, file, " does not exist");
@@ -51,6 +52,14 @@ G4VPhysicalVolume* RMGHardware::Construct() {
       parser.Read(file, false);
     }
     fWorld = parser.GetWorldVolume();
+
+    // Check for overlaps, but with no verbose output.
+    if (!fGDMLDisableOverlapCheck) {
+      RMGLog::Out(RMGLog::summary, "Checking for overlaps in GDML geometry...");
+      auto test_vol =
+          new G4GeomTestVolume(fWorld, 0, fGDMLOverlapCheckNumPoints, /* verbosity = */ false);
+      test_vol->TestOverlapInTree();
+    }
   } else {
     fWorld = this->DefineGeometry();
     if (!fWorld)
@@ -193,6 +202,11 @@ void RMGHardware::DefineCommands() {
       .SetStates(G4State_PreInit)
       .SetToBeBroadcasted(false);
 
+  fMessenger->DeclareProperty("GDMLOverlapCheckNumPoints", fGDMLOverlapCheckNumPoints)
+      .SetGuidance("Change the number of points sampled for overlap checks")
+      .SetStates(G4State_PreInit)
+      .SetToBeBroadcasted(false);
+
   fMessenger->DeclareMethod("IncludeGDMLFile", &RMGHardware::IncludeGDMLFile)
       .SetGuidance("Use GDML file for geometry definition")
       .SetParameterName("filename", false)
diff --git a/tests/basics/CMakeLists.txt b/tests/basics/CMakeLists.txt
index 15393a8d..d85d924e 100644
--- a/tests/basics/CMakeLists.txt
+++ b/tests/basics/CMakeLists.txt
@@ -27,3 +27,10 @@ set_tests_properties(${_macros_extra} PROPERTIES LABELS extra)
 
 list(TRANSFORM _macros_vis PREPEND "basics/")
 set_tests_properties(${_macros_vis} PROPERTIES LABELS vis)
+
+# further specific tests.
+
+# expect two overlaps from this prepared geometry.
+add_test(NAME basics/overlaps.mac COMMAND remage-cli -- macros/overlaps.mac)
+set_tests_properties(basics/overlaps.mac PROPERTIES PASS_REGULAR_EXPRESSION
+                                                    "GeomVol1002.*GeomVol1002")
diff --git a/tests/basics/gdml/overlaps.gdml b/tests/basics/gdml/overlaps.gdml
new file mode 100644
index 00000000..016563c6
--- /dev/null
+++ b/tests/basics/gdml/overlaps.gdml
@@ -0,0 +1,32 @@
+<?xml version="1.0" ?>
+<gdml xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://service-spi.web.cern.ch/service-spi/app/releases/GDML/schema/gdml.xsd">
+	<define/>
+	<materials/>
+	<solids>
+		<box name="World" x="10" y="10" z="10" lunit="m"/>
+		<box name="Box" x="1" y="1" z="1" lunit="m"/>
+	</solids>
+	<structure>
+		<volume name="Box">
+			<materialref ref="G4_Pb"/>
+			<solidref ref="Box"/>
+		</volume>
+		<volume name="World">
+			<materialref ref="G4_Pb"/>
+			<solidref ref="World"/>
+			<physvol name="Box1">
+				<volumeref ref="Box"/>
+				<position name="Box_pos" x="0" y="0" z="0" unit="m"/>
+				<rotation name="Box_rot" x="0" y="0" z="0" unit="rad"/>
+			</physvol>
+			<physvol name="Box2">
+				<volumeref ref="Box"/>
+				<position name="Box_pos" x="0" y="0.5" z="0" unit="m"/>
+				<rotation name="Box_rot" x="0" y="0" z="0" unit="rad"/>
+			</physvol>
+		</volume>
+	</structure>
+	<setup name="Default" version="1.0">
+		<world ref="World"/>
+	</setup>
+</gdml>
diff --git a/tests/basics/macros/overlaps.mac b/tests/basics/macros/overlaps.mac
new file mode 100644
index 00000000..da5ba72a
--- /dev/null
+++ b/tests/basics/macros/overlaps.mac
@@ -0,0 +1,2 @@
+/RMG/Geometry/IncludeGDMLFile gdml/overlaps.gdml
+/run/initialize