Seventeen patients with metastatic disease from malignant melanoma received treatment with injections of Human lymphoblastoid interferon. Fifteen of these had the drug by intramuscular injections. One started treatment by the intramuscular route but later proceeded with slow intravenous infusions. The remaining patient had interferon injected into the tumor only. With one exception, all patients had been pretreated with other methods for advanced regional or blood-borne metastases. A partial response (UICC criteria) lasting six months was seen in one patient who was treated with intramuscular injections for intransit cutaneous metastases in one leg. Human lymphoblastoid interferon appears to have minimal activity relating only to skin metastases in advanced and previously treated malignant melanoma. This activity is not superior to existing treatments.