Many cutaneous disorders are associated with acquired immunodeficiency syndrome. We prospectively evaluated eighteen patients with acquired immunodeficiency syndrome and twelve patients with the immunodeficiency syndrome-related complex for dermatologic disorders. A high prevalence of seborrheic dermatitis was found in patients with acquired immunodeficiency syndrome--83%, in comparison with 1% to 3% of historic control subjects. Patients with the related complex also had an increased incidence of 42%. Seborrheic dermatitis in this population was often more explosive, inflammatory, and severe than is usually seen in otherwise healthy patients. Severity of seborrheic dermatitis correlated with a poor overall prognosis in our patients. Additionally, seborrheic dermatitis may be one of the most common cutaneous manifestations of acquired immunodeficiency syndrome.