Our aim was to define a subgroup of patients with HIV at risk of adverse outcomes in terms of psychosocial factors in order to improve the targeting of hospital resources. The International Classification of Diseases, 9th Revision (ICD-9) coded discharges of all inpatients with HIV discharged from a tertiary hospital between July 1996 and March 1999 were matched against variables in the HIV/AIDS database. A 'prolonged hospitalization' subgroup was defined as those patients whose cumulative length of stay exceeded 90 days in the 33-month period. There were 2778 non-day stay discharges (n=757 patients) constituting 21,286 bed-days. The prolonged hospitalization group (n=62) accounted for 44.3% of the bed-days. Psychosocial co-diagnoses were associated with prolonged hospitalization in both crude and adjusted logistic analyses. These included psychiatric diagnoses such as mania, psychosis and anxiety, HIV dementia, housing issues and the need for social work interventions. In conclusion, a small group of individuals at risk of adverse outcomes has been defined by markers of psychosocial dysfunction. Increased understanding of this group should enable the development of programmes directed at morbidity and mortality.