In the treatment of the classical and endemic African forms of Kaposi's sarcoma (KS), radiation therapy and chemotherapy have been widely used with varying degrees of success and morbidity. We here report our preliminary experiences with low doses of recombinant interferon alfa-2b (rIFN alpha-2b) in the treatment of these types of KS, non-linked to the acquired immunodeficiency syndrome (AIDS). Ten consecutive patients (eight patients with classical and two with endemic KS) with a median age of 62 years were treated long-term with 5 X 10(6) units of rIFN alpha-2b (Introna) given subcutaneously three times weekly for at least 6 months. Of the 10 patients, six presented with cutaneous disease only, and four had additional visceral involvement. After 6 months of treatment, seven of the 10 patients had a major response of the cutaneous lesions, and three patients showed stable skin diseases. Of the four patients with additional visceral disease, one patient showed a complete regression of an intramyocardial tumor involving the right atrium and ventricle, whereas in the three other patients stabilization of the visceral lesions with marked symptomatic improvement occurred. On the whole, the long-term results over a median duration of 12 months (range, 7 to 30) are also satisfactory: IFN-alpha continued to control KS in all patients. The treatment was generally well tolerated; no serious side effects were observed. Our preliminary data suggest that low-dose rIFN alpha-2b regimens are effective in classical and endemic African KS. However, further studies are needed to establish the exact role for IFN-alpha as alternative to radiation and chemotherapy.