Fifteen patients with advanced malignancy were treated with escalating doses of recombinant beta ser 17 interferon (IFN). Doses ranging from 0.006 to 500 X 10(6) units/m2 were administered according to a dosage escalation scheme by iv push twice weekly (starting 1 week after an initial dose) for a planned minimum of 5 weeks, to be continued as a function of response. Toxic effects were broad in scope but generally low in grade. They included fever, malaise, leukopenia, proteinuria, nausea/vomiting, diarrhea, and mild elevations of serum transaminases and creatinine. In one patient, transient hypotension with bradycardia ensued. Malaise and fever increased somewhat with increasing dose. Doses of up to 500 X 10(6) units/m2 were tolerated without severe toxicity. A maximum tolerated dose was not defined. IFN pharmacokinetics followed a biphasic decay curve, with a distribution phase alpha-half-life of 9 minutes and an elimination phase beta-half-life of 103 minutes. Anti-IFN antibodies by the ELISA technique were present in seven of 15 patients. Presence of antibody did not correlate with toxicity or response. 2',5'-Adenylate synthetase levels were increased 2 and 24 hours after the initial dose, with a trend toward higher increments with higher doses. Minimal anti-tumor responses were seen in two patients with melanoma.