Unkept outpatient appointments are a drain on resources. In a prospective study we asked non-attenders at a gastroenterology clinic why they had missed their appointment. 103 patients missed their appointment (14% of the total invited); 3 had died. The remaining 100 were asked to complete questionnaires, 68 by mail (43 returned) and 32 by telephone (30 successful); the response rate was thus 73%. 49 of the respondents were new patients, 6 of them with urgent referrals. The explanations for non-attendance by the 73 patients were: forgot to attend or to cancel (30%); no reason (26%); clerical errors (10%); felt better (8%), fearful of being seen by junior doctor (3%); inpatient in another hospital (3%); miscellaneous other (20%). 13 (27%) of the review patients had not kept one or more previous appointments. The non-attendance rates for different clinics ranged from 10% to 25% (average 14%). A substantial number of non-attenders claimed to have forgotten their appointment or to cancel it. If, as we surmise, this reflects apathy, no strategy to improve attendance is likely to have great impact. Since the non-attendance rate is reasonably constant, it can be taken into account when patients are booked.