Expert clinical reasoning is a vital skill for occupational therapists, particularly in today's rapidly changing health care environment. Clinical reasoning may be the strongest building block of the profession as it diversifies and grows to meet the challenges of the new millennium. Therefore, it is a critical time to continue the research to understand, further develop, and expand occupational therapy's knowledge of clinical reasoning. This article describes the development of the occupational therapy clinical reasoning process and compares it to that of medicine and nursing.