CCNU (1-[2-chloroethyl]-3-cyclohexyl-1-nitrosourea, NSC-79037) was used to treat advanced malignancies in 329 evaluable patients. The treatment dosage was 130 mg/m2 for patients with adequate bone marrow reserve and 100 mg/m2 for those with compromised bone marrow. Oral treatment was repeated at 6-week intervals unless hematologic toxicity intervened. There were four complete responses: two in ovarian cancer, one with small cell carcinoma of the lung, and one with melanoma. Tumor response greater than 50% reduction in tumor size occurred in 39 patients (11.9%) while stable disease (no change or decrease or increase of less than 50% in tumor size) was noted in 152 patients (46.2%). Tumor progression occurred in 130 cases. Melanomas and ovarian and lung cancers had the highest response rates. Bone marrow depression was the major side effect of treatment; there was a significant positive correlation between the severity of leukopenia and thrombocytopenia and tumor response to treatment.