OBJECTIVE: To determine if corticosteroids administered in addition to antimicrobials improve survival in children with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia (PCP). DESIGN: Before-after, nonrandomized, case-comparison study. SETTING: Pediatric intensive care unit of a tertiary care teaching hospital in Florida. PARTICIPANTS: Eleven children infected with the human immunodeficiency virus (HIV) with confirmed PCP. SELECTION PROCEDURE: Infants with HIV infection and acute respiratory failure due to PCP were studied sequentially. INTERVENTION: The first seven infants were treated with antimicrobials alone while the next four received a 2-week course of methylprednisolone sodium succinate in addition to antimicrobials. MEASUREMENTS AND RESULTS: The two groups were similar with respect to age, route of HIV infection, stage of HIV disease, CD4 T-cell count, antiretroviral therapy, and respiratory parameters at intubation. All children treated with antimicrobials alone died while receiving mechanical ventilation. Survival of the children who received corticosteroid therapy was significantly improved (P < .05), and all were weaned from the ventilator. CONCLUSIONS: Corticosteroids administered in addition to antimicrobials and supportive care improve the short-term survival of HIV-infected children who have acute respiratory failure due to PCP.