To evaluate the safety and effectiveness of trimetrexate (TMTX) given at increasing doses along with the leucovorin calcium (LCV) for treating Pneumocystis carinii pneumonia (PCP) in AIDS patients TMTX is an experimental new drug which is effective for treatment of PCP, but has been given to only a few patients. Therefore it is not certain if TMTX is better, the same as, or not as effective as conventional drugs against PCP.

TMTX is an experimental new drug which is effective for treatment of PCP, but has been given to only a few patients. Therefore it is not certain if TMTX is better, the same as, or not as effective as conventional drugs against PCP.

Increasing doses of TMTX are used in combination with LCV as initial treatment for PCP in 50 AIDS patients. Doses are increased for 21 days on a once daily and then a twice daily basis. Dose escalations occur in subsequent groups of patients.

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.