I have installed mpich-3.04 on a computer powered by linux. Everything seems to be OK. The example in f.90 runs correctecly without error mesages. When I try my own trial code (simply a send and a recv call) I get the following error mesage : Assertion failed in file src/mpid/ch3/src/mpid_vc.c at line 140: MPIU_Object_get_ref((vcrt)) >= 0 The process which aborts is the one on which I use the recv instruction. I have use mpiexec -n <n> ./trial.out I have tried with ifort and gfortran compilers with the same result. I have made the same install on another computer also powered by Linux with exactly the same result. The 2 Linux are different: Fedora 19 and RedHat Enterprise 6.2 Thank you for your help. VR