If there is any question about whether these calls are still valid after an error with an error handler that returns (MPI_ERRORS_RETURN or user handler) MPI_Abort, MPI_Error_string MPI_Error_class I assume it should be corrected as a trivial oversight in the original text. I would regard the real issue as being the difficulty with assuring the state of remote processes. There is huge difficulty in making any promise about how an interaction between a process that has not taken an error and one that has will behave. For example, if there were a loop of 100 MPI_Bcast calls and on iteration 5, rank 3 uses a bad communicator, what is the proper state? Either a sequence number is mandated so the other ranks hang quickly or a sequence number is prohibited so everybody keeps going until the "end" when the missing MPI_Bcast becomes critical. Of course, with no sequence number, some tasks are stupidly using the iteration n-1 data for their iteration n computation. Dick Treumann - MPI Team IBM Systems & Technology Group Dept X2ZA / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601 Tele (845) 433-7846 Fax (845) 433-8363