Shared-memory multiprocessors have received wide attention in recent times as a means of achieving high-performance cost-effectively. Their viability requires a thorough understanding of the memory access patterns of parallel processing applications and operating systems. This paper reports on the memory reference behavior of several parallel applications running under the MACH operating system on a shared memory multiprocessor. The data used for this study is derived from multiprocessor address traces obtained from an extended ATUM address tracing scheme implemented on a 4-CPU DEC VAX 8350. The applications include parallel OPS5, logic simulation and a VSLI wire routing program. Reprints.