A Study of Trimetrexate in the Treatment of Pneumocystis Carinii Pneumonia (PCP) in Patients With AIDS Not Previously Treated for PCP

Inclusion Criteria Patient must: * Have Pneumocystis carinii pneumonia (PCP) that has not been treated for current episode. PCP must be documented by observation of \> 1 cluster of organisms in sputum, bronchial secretion, or lung tissue. * Have clinical symptoms of respiratory disease or radiologic abnormalities. Exclusion Criteria * Patient cannot have significant emotional disorder. Concurrent Medication: Excluded: * Drugs likely to be bone marrow toxic. * Investigational drugs. Prior Medication: Excluded: * Three patients in each group cannot have had zidovudine (AZT) for at least 2 months prior to administration of trimetrexate.