Patient dropouts create inefficiencies for medical providers, threaten the validity of clinical research and may themselves suffer unnecessary morbidity. A review of literature concerning patient dropouts and broken appointments was undertaken in an effort to identify correlates of the behavior, assess proposed interventions and identify issues for the content and methodology of future research. While the bulk of existing reports deal with psychiatric and pediatric populations, studies of general adult clinics report missed appointments rates of 15 to 33 per cent and often emphasize demographic features of the patient. Other factors, such as patient beliefs, sociobehavioral characteristics, aspects of the disease and its therapy, patient-provider interactions and organizational features of the providing facility are less well studied, but probably more important. Organizational features exert a strong influence and are particularly amenable to modification. Patient surveys suggest that forgetting and administrative oversights are common problems, and the success of mailed appointment reminders supports this notion. Such surveys have often suggested successful intervention strategies. Future investigations should emphasize more consistent methodology, improved analysis techniques, identification of better predictors and development of a conceptual model for this patient behavior. These efforts may suggest new intervention methods, which should be evaluated for cost effectiveness and the feasibility of individualized application.