Failure of patients to attend outpatient clinics is common and costly. In one consultant's general medical and gastrointestinal outpatient clinic, 38% of new patients failed to keep at least one appointment, 17% did not attend for their first outpatient consultation and, of these, 59% failed to keep a second appointment sent to them. Of the patients who did attend for their first consultation 12% did not keep their next two appointments. Failure to attend was more common in men, young patients, patients from certain inner city areas, patients on the lists of certain general practices, and those who had already defaulted once. Possible background reasons for default are discussed, suggestions for further study proposed, and an attempt made to look for ways to reduce the extent of the problem.