Twenty patients with soft tissue sarcoma were treated with iv human fibroblast interferon (beta-interferon). Each cycle of treatment involved 5 X 10(6) units over 10 minutes, then 5 X 10(6) units iv over 3 hours daily X 10 with cycles repeated every 20 days X 3. Maintenance therapy was given twice weekly if disease was stable or responsive after three therapy periods. One patient had a partial response to treatment and six patients experienced stable disease for variable periods of time. Toxicity (fever, fatigue, leukopenia, hepatic enzyme elevations) was moderate and tolerable; therapy (except in one case of profound granulocytopenia) was neither interrupted nor discontinued because of toxicity. We conclude that beta-interferon in the dose and schedule used has limited value for soft tissue sarcoma.