Twenty patients with HIV infection and mania were grouped according to whether their first manic episode occurred when CD4 count was or = 200 (early onset). The late-onset patients were less likely to have personal or family histories of mood disorder and more likely to have dementia or cognitive slowing. They also exhibited a different manic symptom profile. The different sociodemographic and symptom profiles associated with early-onset and late-onset mania may reflect differences in pathophysiology.