A new tracing feature in PVM now directly supports the tracing of PVM programs. In this section we describe the tracing feature and present a tool, XPVM, which displays PVM trace information. Tracing is a popular way of debugging parallel programs. There have been many systems which support program tracing for debugging [10]. More recently systems such as Pablo [11], Paragraph [7], PICL [6], Bee [3], and Xab [2][1] have been developed to aid the parallel programmer. Pablo, Paragraph, and Bee are intended to be general tools for displaying trace information for parallel programs. PICL is a communication library for multicomputers which is portable and generates tracefiles. Xab is a specific tool for tracing PVM programs. Xab will generate and display traces of PVM programs. XPVM and the new tracing feature of PVM are based on the previous work done on Xab.