Eighteen patients with advanced breast cancer refractory to first-line chemotherapy and hormonal therapy (or estrogen receptor-negative) were treated with human alpha-lymphoblastoid interferon (Wellferon) in a dose of 30 X 10(6) U/m2 im weekly. None of 15 patients receiving three or more doses achieved a partial or complete response. Toxicity was substantial and included fatigue, malaise, fever, hematologic suppression, nausea/vomiting, and diarrhea.