<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Hi Ida, Simon I have checked my root/include directory and this is where all .h header files are located (I don't have another root directory inside include directory). My problem was about ROOTSYS environmental variable and scrip I was using to set some other variables, here you can read more: http://ubuntuforums.org/showthread.php?t=1290178 I'm still not sure how I got it working, but it works now . I have then started compilation process, and this is my output at the end Compiling GateUIterminal.cc ... Compiling GateVisAttributesMessenger.cc ... Compiling GateVisManager.cc ... Compiling GateXMLDocument.cc ... source/management finished Creating/replacing object files in ./tmp/Linux-g++/Gate/libGate.a ... ar: creating ./tmp/Linux-g++/Gate/libGate.a Compiling Gate.cc ... In file included from ./source/mandatory_G4_classes/include/GateRunManager.hh:46,                  from Gate.cc:18: /usr/share/geant4/geant4.9.2.p01/source/run/include/G4RunManager.hh: In member function ‘void G4RunManager::SetRandomNumberStoreDir(G4String)’: /usr/share/geant4/geant4.9.2.p01/source/run/include/G4RunManager.hh:352: warning: ignoring return value of ‘int system(const char*)’, declared with attribute warn_unused_result Using granular libraries ... Linking Gate ... ... Done! There were some warn_unused_result warnings, but I'm not sure if this is a serious problem. If this is a successful compilation how do I start Gate, or some examples ? I have tried to type "Gate" and "Gate benchmarkPET.mac" at command prompt but I got "bash: Gate: command not found" regards Marko </td></tr></table>