This paper makes the point that for psychiatric patients the nursing process based on a systems approach may be more useful than that based on problem-solving or activities of daily living. Some of the key concepts used in this approach are (1) listing component parts of a system, (2) defining the inside and outside of systems, the outside being described as environment, (3) changing the boundaries or the interface of various systems, as appropriate, (4) observing the impact of the environment and especially of the nurse herself as a part of the system or the environment, (5) tracing input, output and throughput, and (6) drawing distinctions between open and closed systems and accounting for a steady state in the system.