Two hundred and twenty six consecutive patients aged over 75 years discharged following an acute medical admission to a district general hospital were followed up six months later. 46 (20.3%) required emergency admission within three months of discharge. 19 had a diagnosis related to their original admission, and 27 an unrelated diagnosis. The mean time to readmission was 34 days, but this was significantly shorter (21 days) in those with a related diagnosis. Those readmitted had more often required admission in the year prior to their index admission, had more comorbidities, higher use of social services, and no carer. There were no significant differences in age, gender, mental test score, length of stay, home circumstances or diagnosis. The results suggest that most readmissions are due to medical rather than social problems, and that most are unavoidable. Efforts to reduce readmissions should be directed at preventing early medical relapse in at risk patients.