This prospective randomized Eastern Cooperative Oncology Group (ECOG) study (1071) was designed to compare a new and promising cytotoxic agent TIC Mustard (triazeno imidazole carboxamide mustard, NSC 82196) with DTIC (dimethyl triazeno imidazole carboxamide, NSC 45388) in the treatment of inoperable melanoma. One hundred and seventy-eight patients were randomized to receive either DTIC (150 mg/m2/day X 5) or TIC Mustard (800 mg/m2/day X 5). Of this group 145 patients were evaluable for tumor response at the completion of the study. Objective responses were seen in 15/79 (19.0%) DTIC patients and 4/66 (6.1%) TIC Mustard patients. Adjustment of crude response rates yielded final response rates of 18.2% for DTIC patients and 5.8% for TIC Mustard. These differences were significant at the p less than or equal to .03 level. Median response duration was 15 weeks for the DTIC responders and 4 weeks for the TIC Mustard responders. Responders and nonresponders did not differ significantly in any of the standard prognostic categories. However, responders had a significantly longer median survival (47.5 weeks) compared to that for nonresponders (17.8 weeks). Toxicity was tolerable for either drug and no deaths were ascribed to either. We conclude that TIC Mustard has limited usefulness in the treatment of malignant melanoma and is less effective than DTIC.