A Compassionate Treatment Protocol for the Use of Trimetrexate Glucuronate With Leucovorin Protection for Patients With Pneumocystis Carinii Pneumonia.

Inclusion Criteria Concurrent Medication: Allowed: * Antiretroviral therapy (at the discretion of the treating physician and/or medical monitor). Patients must have: * Presumptive or definitive diagnosis of Pneumocystis carinii pneumonia (PCP). * HIV positivity or be otherwise immunosuppressed. * Demonstrated intolerance and/or resistance to trimethoprim/sulfamethoxazole during the course of therapy for the current episode and not candidates for parenteral pentamidine, OR a documented history of such intolerance during a prior episode. * Consent of parent or guardian if less than 18 years of age. NOTE: * In general, patients who meet the eligibility criteria for other U.S. Bioscience-sponsored clinical trials for trimetrexate would not be eligible for this Compassionate Use protocol. Exclusion Criteria Patients with the following prior conditions are excluded: History of Type I hypersensitivity (i.e., urticaria, angioedema, or anaphylaxis), exfoliative dermatitis, or other life-threatening reactions to trimetrexate.