In developing countries, many human immunodeficiency virus (HIV)-infected children require intensive care unit (ICU) resources for pneumonia, but there is little information on the etiology of pneumonia or the impact of ICU intervention. OBJECTIVE: To compare the etiology and outcome of pneumonia in HIV-positive and seronegative children admitted to ICU. DESIGN: Prospective study. SETTING: Two pediatric ICUs linked to the University of Cape Town, South Africa. PATIENTS: Consecutive children admitted for pneumonia during 1998. MEASUREMENTS AND MAIN RESULTS: Clinical, demographic, ventilatory, and laboratory data were collected. Blood for testing was obtained. Induced sputum or nondirected bronchoalveolar lavage was performed for culture and Pneumocystis carinii identification; gastric lavage (GL) provided specimens for mycobacterial culture. Seventy-six children (21 [27.6%, 95% confidence interval {CI} = 18-39.1] HIV-positive) were enrolled. At admission, HIV infection was diagnosed in 15 of the 21 (71.4% [47.8-88.7]) HIV-positive patients. P. carinii pneumonia occurred in eight HIV-positive children (38% of HIV-infected patients) and one HIV-negative child. It was the acquired immunodeficiency syndrome (AIDS)-defining illness in seven children (47%). The incidence of bacteremia (15.3%) was similar in HIV-positive (15.8%) and HIV-negative children (15.1%), p =.94; Streptococcus pneumoniae and Staphylococcus aureus were the predominant isolates. Bacterial and viral isolates from sputum or bronchoalveolar lavage, including Mycobacterium tuberculosis in six (8%) children, did not differ by HIV status. Intermittent positive pressure ventilation was used in 8 of 21 (38%) HIV-positive children and 28 of 55 (51%) HIV-negative children, p =.32. Median days of intermittent positive pressure ventilation (3 [2-6]), ICU (5 [3-9.5]), and hospital (11 [7.5-19]) did not vary by HIV status. The in-hospital mortality rate for HIV-positive children (6 of 21 [28.6%]) was double that for seronegative patients (8 of 55[14.5%], relative risk [RR] 1.96 [0.77-4.99], p =.16). CONCLUSION: More than a quarter of children admitted to ICU for pneumonia in this geographic area are HIV-positive; most are diagnosed with HIV at admission. P. carinii pneumonia is a common AIDS indicator disease. HIV-infected children admitted with pneumonia had a worse outcome than seronegative children, a difference that is rendered statistically insignificant by the small sample size.