Retrospective analysis of 2,745 psychiatric admissions over 5 yrs showed a consistent excess of male over female inpatients by a ratio of 1.49:1. To explore this phenomenon, 80 male and 44 female admissions over 3 mo were prospectively assessed, using a modified form of the Bethlem Royal and Maudsley Hospital observation sheet. The assessment included sociodemographic characteristics, personal, medical and psychiatric history, symptom profile and investigations, and treatment outcome as assessed by the Clinical Global Impression Scale. Male Ss had more often sought contact with psychiatric services and had more frequent previous admissions than female Ss. Apart from birth order, no differences were found in circumstances of upbringing or development. Male Ss with a psychotic disorder more often exhibited delusions of persecution, and received a diagnosis of schizophreniPatients admitted for alcohol and drug related problems were exclusively males. On the other hand an increasing number of female Ss presented with affective and conversion symptoms and received diagnoses of affective disorder and conversion disorder, Female Ss were more often considered to be markedly improved on discharge than male Ss, perhaps due to the different diagnostic profile.