A total of 55 patients were treated with ifosfamide on two different treatment schedules. Twenty-four patients (22 with bronchogenic carcinomas and two with metastatic lung tumors) received 50 mg/kg of ifosfamide each day for three consective days, every three weeks (Regimen I), and the remaining 31 patients (24 with bronchogenic carcinomas and seven with metastatic lung tumors) received 40 mg/kg each day for five consective days, every three weeks (Regimen II). All patients had disseminated cancer, and 20 had had prior chemotherapy. Of the 20 evaluable patients with bronchogenic carcinoma who underwent Regimen I, five patients with small cell carcinoma had positive responses (one complete and four partial), whereas seven patients with other histologic cell types did not respond to the treatment. Of two metastatic lung tumor patients under Regimen I, one with cervical carcinoma had a partial response. The overall response rate for Regimen I was 6/22 (27%). With Regimen II, of 22 evaluable patients with bronchogenic carcinoma, nine (seven with small cell carcinoma, one with adeno carcinoma and one with squamous cell carcinoma) had partial responses. Of seven evaluable patients with metastatic lung tumor, two patients with cervical carcinoma had positive responses (one complete and one partial). The overall response rate for Regimen II was 11/29 (38%). Myelosupressive toxicity was mild: leukopenia (less than 2,000/cmm) occurred in 12% of the patients under Regimen I and 6% under Regimen II, and thrombocytopenia (less than 100,000/cmm) in 12% under Regimen I and 3% under Regimen II. Bladder toxicity occurred in 50 % of the patients under Regimen I and 52% under Regimen II. Upper gastrointestinal symptoms, such as nausea and vomiting occurred in one half of the patients under either Regimen. In conclusion, there were no significant differences in response rate and toxicity between the two treatment schedules. Ifosfamide appears effective in the management of disseminated cervical carcinoma, as well as small cell lung carcinoma. The agent should be considered in combination with other active agents in the treatment of bronchogenic carcinoma.