Ninety-six patients with disseminated malignant melanoma received thrice weekly intramuscular injections of leukocyte A recombinant interferon (rIFN-alpha A, Roferon-A, Hoffmann La Roche) at doses of 12 X 10(6) U/m2 or 50 X 10(6) U/m2 with or without cimetidine as an immunorestorative agent. Four patients, two with prior chemotherapy, demonstrated either a complete response (3 months, soft tissue metastasis) or exceptionally durable response durations (months) of 29+ (soft tissue; lung lesion), 31+ (soft tissue), and 35+ (soft tissue; liver lesions). None of these patients had particularly characteristic clinical parameters. As noted previously, using chemotherapy, a small proportion of patients with advanced malignant melanoma, despite prior therapy, may achieve prolonged objective regression with rIFN-alpha A.