Several aspects of the multidimensional problem of providing monitoring support tools for the debugging and performance analysis of software for distributed and parallel systems are presented. A formal event-action model at the process level and a layered architectural model are introduced. The application of the event-action model to the development of the layered architectural model is shown. This effort was motivated by the need to understand the ways in which a monitoring system may intrude upon a monitored system. An understanding of the fundamental ideas underlying the relationship between monitoring and monitored systems is necessary to build practical tools for software development. These models are currently being used in the development of monitoring tools for the PASM parallel processing system prototype. © 1990.