The clinical presentation, radiological and laboratory evaluation, treatment, and risk factors of sinusitis in a cohort of 376 human immunodeficiency virus (HIV)-infected children from a placebo-controlled clinical trial of intravenous immunoglobulin (IVIG) as prophylaxis for infections were examined. Ninety-five episodes of sinusitis were described in 60 patients; one-third of the patients had two or more episodes. Sinusitis episodes were commonly associated with nonspecific, chronic symptoms (67.4%, persistent nasal discharge; 54.7%, nocturnal or persistent cough), whereas symptoms more specific to acute sinusitis were less frequent (17.9%, headache or facial pain; 9.5%, periorbital swelling; 25.3%, temperature of > or = 102 degrees F; 9%, total white blood cell count of > or = 15,000/mm3). The sinuses primarily involved were the maxillary sinus (85.9%) and the ethmoidal sinus (42.3%); 36% of episodes involved two or more sinuses. Preceding respiratory infections did not appear to increase the risk of sinusitis, and CD4+ lymphocyte counts in children with and without sinusitis did not differ. Neither monthly IVIG prophylaxis nor three times weekly trimethoprimsulfamethoxazole prophylaxis for Pneumocystis carinii pneumonia decreased the risk of sinusitis. Sinusitis in HIV-infected children is most often subacute and recurrent. Evaluations of new modalities for prophylaxis for sinusitis are needed.