The response of 18 patients with metastatic malignant melanoma to the combination of CCNU (130 mg/m2) preceded 3-4 hr earlier by 20 mg/kg of the 2-nitroimidazole benznidazole has been studied. There were four partial and no complete responses in 16 patients evaluable after 1-6 courses. The median response duration was 14 wk (range 5-33) and for static disease 24 wk (range 10-54). Evidence for chemosensitization is equivocal.