Ninety-six patients with advanced malignant melanoma received thrice weekly im recombinant leukocyte A interferon (Roferon-A) in three consecutive phase II trials utilizing doses of 12 X 10(6) U/m2, 50 X 10(6) U/m2, and 50 X 10(6) U/m2 plus cimetidine. The overall response rate was 22%, with median times to disease progression and survival of 3.9 and 11.3 months, respectively. For all study participants, the median times to disease progression and survival were 1.5 and 5 months, respectively. Most regressions occurred within the first month of treatment and were predominantly in soft tissue, although three patients are responding 2-3 years after onset of treatment. The most noteworthy toxic effects included a flu-type illness, anorexia, and fever (38.3-39.4 degrees C). The median weight loss was 2.1 kg on the low-dose regimen and 5.6 kg on the high-dose program. Recombinant leukocyte A interferon in the dosages and schedule that we used has definite but limited efficacy for patients with disseminated malignant melanoma.