Coordination is a hallmark of primary care. Efforts to improve primary care services should involve assessment of the extent to which coordination is achieved. Our study in three adult and three pediatric clinics demonstrates that existing information concerning patients' problems, therapies, tests, and referrals is often not recognized by primary care practitioners. Recognition of these types of information is better when the practitioner who provides follow-up care is the same from one visit to the next. Information about visits which were anticipated by the practitioner, and particularly the content of these visits, is often neglected. The largest deficit, however, is in recognition of both the occurrence and content of visits unanticipated by the primary care practitioner. Greater efforts to achieve better coordination of care, by improving either continuity of practitioner, communication among practitioners, or the information system, are required before this essential element of primary care becomes a reality.