Comparison of Trimetrexate Plus Leucovorin Calcium Rescue Versus Sulfamethoxazole-Trimethoprim in the Treatment of Pneumocystis Carinii Pneumonia (PCP) in Patients With AIDS

Inclusion Criteria Concurrent Medication: Allowed: * Acetaminophen: * 650 mg prescribed as necessary for temperature \> 38.7 degrees C. Acetaminophen should not be prescribed as a standing order for more than 48 hours. Prior Medication: Allowed: * Zidovudine (AZT) as long as such therapy is suspended prior to randomization and not reinstituted until therapy for the acute episode is completed and the patient's white blood cell count is acceptable. * Other myelosuppressive therapies which may be handled in the same manner as AZT. * Prophylaxis for Pneumocystis carinii pneumonia (PCP). * Unequivocal diagnosis of Pneumocystis carinii pneumonia (PCP) by morphologic confirmation of three or more typical P. carinii organisms in sputum, bronchoalveolar lavage fluid, or lung tissue obtained by transbronchial or open-lung biopsy within 3 days before or after randomization. If morphologic confirmation is not possible prior to therapy, patients may be randomized if the investigator believes there is a high suspicion of PCP based on clinical presentation. If morphologic diagnosis cannot be established within 6 days of randomization, the patient will be withdrawn from study therapy. Resting (A-a) DO2 \< 30 torr on room air. Patient, parent, guardian, or person with power of attorney gives informed consent. Exclusion Criteria Co-existing Condition: Patients will be excluded for the following reasons: * History of Type I hypersensitivity (i.e., urticaria, angioedema, or anaphylaxis…