Hi, I try the following code( eg2_clt.cc) Echo_var echoref1 = NULL; if( CORBA::is_nil(echoref1) ) { cerr << "Can't narrow reference to type Echo (or it was nil)." << endl; return 1; } I will get core dump. It seems that CORBA::is_nil can not handle the point of NULL. My machine is HP-HU11 and using aCC3.30. Any advice are greatly appreciated, Best Regards, GY