This revision of the Message Passing Toolkit: PVM Programmer's Manual, supports the 1.4 and 1.5 releases of the Message Passing Toolkit for IRIX (MPT). No technical changes have been made for the MPT 1.5 release. The MPT implementation of PVM for IRIX systems contained in this release is based on the Oak Ridge National Laboratories (ORNL) version 3.3.10.