Medical interviewing is the foundation of medical care and is the clinician's most important activity. A growing body of evidence suggests that clinicians use distinctive, describable behaviors to conduct medical interviews. This article describes four patterns of behavior that we term Habits and reviews the research evidence that links each Habit with both biomedical and functional outcomes of care. The Four Habits are: Invest in the Beginning, Elicit the Patient's Perspective, Demonstrate Empathy, and Invest in the End. Each Habit refers to a family of skills. In addition, the Habits bear a sequential relationship to one another and are thus interdependent. The Four Habits approach offers an efficient and practical framework for organizing the flow of medical visits. It is unique because it concentrates on families of interviewing skills and on their inter-relationships.