Reliability and validity of two clinical simulation tests were studied, using a multimethod approach. The instruments were originally tested in a project that compared ability of physicians, nurse practitioners, and public health nurses to provide primary care. Reliability was assessed by comparing test scores of the same subjects on two occasions. Validity was assessed by: 1) comparing test scores of two expert panels and of professional health groups (nurses and physicians) with preprofessional groups (nursing and medical students), 2) comparing test contents with authoritative literature on the disease, and 3) analyzing results of test evaluation by all subjects. Subjects of the original project were compared with those in this study. Both tests were found reliable and valid, corroborating the original project's findings that nurse practitioners and physicians are equally proficient in assessment and treatment of health problems. Findings also lend validity to the tests' developmental model and suggest the usefulness of such tests in nursing and medical education.