A case-control survey of 136 absconders who left hospital without permission on a total of 170 occasions over a 15-month period was carried out. Absconding tended to be more frequent during the day time shifts (in contrast to the night shifts) and during the weekdays (in contrast to the weekends). The destination in the majority (62.4%) was the home. Absconders differed significantly from non-absconders in terms of a tendency towards being single (p < 0.01), having a current or previous history of drug abuse (p < 0.01), being employed (p < 0.05) and staying longer on admission (p < 0.01). The results were discussed and explanations proffered for the significant differences. Finally, suggestions were made on ways of minimising the frequency of absconding from mental hospitals in the light of the results.