In this comparative study with a control group of prisoners, psychiatric morbidity was measured in two groups of sentenced prisoners, each group completing the GHQ-30 and 21-item Beck Depression Inventory (BDI). Group 1 consisted of 40 segregated HIV-positive prisoners and group 2 a matched control group in the main prison who had no history of HIV seropositivity. All members of group 1 had a history of intravenous drug abuse. The mean GHQ-30 and BDI scores were significantly higher in group 1, and 90% of group 1 were psychiatric 'cases' compared with just over 42% of group 2. Levels of psychiatric morbidity present in a third group, consisting of HIV-positive prisoners who had not been segregated (prison authorities were unaware of their seropositivity) are an interesting pointer for further research.