This paper explores collaborative practice by examining the modes of thought and action that nursing and medicine use in dinical problem solving. The characteristics that define and differentiate nursing and medicine establish the perspectives of the professions, and these perspectives contribute to and limit the two different ways of interpreting reality. In collaborative practice, the set of problems defined by a specific client and by each discipline becomes part of the context of clinical problem solving for both nurses and physicians. Means are suggested to clarify the process of nursing assessment or diagnosis and its relationship to corresponding processes in medicine. Such analysis helps to define the contributions that nursing makes to health care.