One hundred sixty-nine patients with histologic evidence of disseminated malignant melanoma, including patients with cerebral metastases, were entered into a Phase II study of the nitrosourea fotemustine. The treatment regimen consisted of a 100 mg/m2 1 hour IV infusion every week for 3 consecutive weeks, followed by a 4- to 5-week rest period (induction therapy). In responding or stabilized patients, maintenance therapy consisted of 100 mg/m2 every 3 weeks until the disease progressed. One hundred fifty-three patients were evaluable for response. Three complete responses and 34 partial responses were observed (according to the World Health Organization criteria), leading to an objective response rate of 24.2% (95% confidence interval: 17.4% to 31.0%). Responses were also documented on cerebral (25.0%), visceral (19.2%), or nonvisceral (31.8%) metastatic sites. The median duration of response was 22 weeks (range, 7 to 80 weeks). The objective response rate in previously untreated patients was 30.7% (19 of 62 patients). The main toxicity was hematologic with delayed and reversible leukopenia and/or thrombopenia. The objective response rate observed (especially in untreated patients), the activity on cerebral metastases, and the small amount of extra-hematologic toxicity encountered suggest that fotemustine is an effective drug in disseminated malignant melanoma.