Medical diagnosis often depends on the ability of patients to recall and report their medical history. In this study 104 people kept health diaries for 3 months, recording the incidence, frequency, data, duration, and severity of health events (symptoms, illnesses, injuries, visits to health professionals, and medication). Memory for the events recorded was tested immediately after the diary-keeping period or at 1 month or 3 months later. Effects of age, gender, education, health status, anxiety, and retention interval were observed. With a free recall procedure only 47 per cent of health events were recalled. Following the free recall two different kinds of intervention were compared. Use of a recognition checklist yielded recall of 29 per cent of the forgotten events but with a cognitive interview procedure only 6 per cent of the forgotten items were retrieved.