Ametantrone is the third of a family of anthracene derivatives to undergo a phase I trial in man. Sixteen patients received 33 courses of drug as a single iv dose given every 3 weeks. Escalations proceeded from 120 to 180 mg/m2. Predictable and reversible leukopenia was the dose-limiting toxic effect. Four patients developed thrombocytopenia. Nonhematologic toxic effects included a marked cumulative blue discoloration of the skin seen in all patients receiving more than three courses of the drug. This cumulative cosmetic effect may also be dose-limiting. Other nonhematologic toxic effects included: blue urine (all patients), nausea (two), vomiting (one), a blue stool (one), and reversible elevations of either SGOT or alkaline phosphatase (two). No objective responses were seen in this study. A dose of 140-160 mg/m2 is recommended as the starting dose for phase II trials in patients who have received prior chemotherapy or radiotherapy.