A critical aspect of any residency is the process of selection and evaluation. However, the research literature has failed to provide an adequate behavioral specification of performance components to assist in selection and evaluation decisions. In this investigation, we applied a widely accepted method of job analysis from personnel psychology, the critical incident technique, to define those behaviors and attitudes necessary for successful resident performance in obstetrics and gynecology. Nine mutually exclusive categories of behavior were identified, including conscientiousness, recognition of limits, confidence in skills and training, ability to handle crisis/emergency situations, integration of knowledge with practice, technical skills, relationships with staff, relationships with patients, and ethical actions. These categories appear to be reliable, as physician raters were able to sort incidents into appropriate categories with 94% reliability. Identification of these categories represents a beginning step toward determining necessary aspects of performance in a structured and replicable manner and toward defining these performance aspects in a manner that allows precise and reliable measurement.