AMENDED: 08/01/90 As of August 31, 1989, 437 patients were enrolled into uncontrolled studies of trimetrexate for PCP:214 in TX 301/ACTG 0=039 (trimetrexate for patients intolerant of approved therapies) and 223 in NS 401 (trimetrexate for patients refractory to approved therapies). The analysis of overall response rate, stringently defined as having received at least 14 days of trimetrexate and being alive at follow-up 1 month after the completion of therapy, reveals 84/159 intolerant patients and 48/160 refractory patients had responded, for rates of 53 percent and 30 percent, respectively. These response rates include all individuals who received at least one dose of trimetrexate. Of the 111 patients who were ventilator-dependent at study entry, 18 completed a course of therapy and were alive a month later, for a response rate of 16 percent. All other ventilated patients died. The most common severe (grades 3 and 4) toxicities were: transaminase elevation (> 5 x normal) in 94 patients, anemia (< 7.9 g/dl) in 109, neutropenia (< 750 cells/mm3) in 58, fever (> 40 C) in 37, and thrombocytopenia (< 50000 platelets/mm3) in 27. Toxicity required discontinuation of therapy in approximately 5 percent of all patients.