Autonomic function tests have been recorded in 40 male homosexual patients with serum antibodies to human immunodeficiency virus (HIV) and 12 male homosexuals without such antibodies. Abnormalities of autonomic function were found in 15 of 31 patients without other recognized reasons for autonomic dysfunction. Four patients had two or more test abnormalities. The profile of these abnormalities was found to be different from that of autonomic neuropathy associated with diabetes and other disorders and was consistent with the presence of sympathetic overactivity. Abnormalities in autonomic function were particularly associated with clinically identifiable neurological complications of HIV infection.