Fifteen evaluable patients with metastatic malignant melanoma who had received no prior chemotherapy were treated with high-dose cimetidine orally, 600 mg q.i.d. Although three patients had stable disease lasting 2–4 months, there were no objective responses. Median survival was 5.3 months (range 1–18 months). Toxicity was essentially negligible except for severe diarrhea in one patient and worsening liver function abnormalities in another. High-dose cimetidine does not have any significant activity in metastatic melanoma.