In March of 1972, the Southwest Oncology Group initiated a Phase II study, No. 7200, utilizing methyl-CCNU in the treatment of patients with solid tumors and lymphomas. Initially, they received 200 mg/m2 orally as a single dose every 6 weeks. The dose was subsequently reduced in poor-risk patients to 150 mg/m2. There were 69 responses noted in 675 evaluable patients (10%). The highest response rates were noted in patients with Hodgkin's disease (13/31, 35%), malignant gliomas of the brain (8/29, 28%), anaplastic carcinomas of the lung (5/20, 25%), and squamous cell carcinomas of the head and neck (5/29, 17%). Squamous cell tumors appeared to be more responsive than adenocarcinomas (15% vs. 5%, respectively). Hematologic toxicity was cumulative, and was influenced by dose and prior treatment. There appeared to be no cross-resistance in patients previously treated with alkylating agents. Methyl-CCNU is an active antineoplastic agent. Further studies are indicated in order to determine relative effectiveness.