On Linux, I get a segmentation fault as soon as I run one of the official examples. Check that the CLHEP library has been installed and compiled coherently with the same compiler you use for installing Geant4 and for the same version of Linux distribution. For example, a binary object produced with Red-Hat 7.X is not fully compatible with binaries running on RH 9.X or higher, due to different libc used in the two configurations. I installed Geant4 libraries and built my application, when I try to run it I get: error in loading shared libraries: libCLHEP.so: cannot open shared object file: No such file or directory. Your installation of CLHEP includes shared libraries. You need to specify the path where libCLHEP.so is installed through your environment variable LD_LIBRARY_PATH. For example, in tcsh UNIX shell: setenv LD_LIBRARY_PATH ${LD_LIBRARY_PATH}:$CLHEP_BASE_DIR/lib On my system I get a Floating Point Exception (FPE) since some physics processes sometimes return DBL_MAX as interaction length and this number is afterwards multiplied by a number greater than 1. Geant4 coding conventions and installation setup explicitly follow the ANSI/IEEE-754 Standard for the initialization of floating-point arithmetic hardware and portability. The Standard foresees floating-point arithmetic to be nonstop and underflows to be gradual. On DEC platforms, for example, the ANSI/IEEE-754 Standard compliance needs to be explicitly set (since deactivated by default); in this case we use infact the option "-ieee" on the DEC/cxx native C++ compiler to achieve this. You should check if your compiler provides compilation options for activating Standard initialization of FP arithmetic (it may be platform specific).