Patient characteristics, chief complaints, and diagnoses can be used to specify the examination content for performance-based assessments of clinical skills. The purpose of this investigation was to explore osteopathic and allopathic medical practice patterns and to provide summary statistics that can be used to delimit potential assessment content areas for a clinical skills assessment targeted at osteopathic physicians. Analyses of the National Ambulatory Medical Care Survey indicated that the types of patients seen by osteopathic and allopathic physicians in office-based settings are somewhat different. Furthermore, the reasons that patients seek care, and accompanying diagnostic outcomes, can vary by physician type. These differences suggest that from a content perspective, a performance-based clinical skills evaluation targeted at osteopathic physicians should be characteristically different from one designed for allopathic physicians.