A phase I clinical trial was conducted with recombinant human tumour necrosis factor alpha (rhTNF-alpha) in 62 patients with advanced malignancy refractory to previous standard therapy. rhTNF-alpha was given as a 30 min infusion twice a day at 6 h intervals. A total of 10 different dose levels was escalated in cohorts of 6 patients ranging from 2.5 to 200 micrograms/m2 twice a day for 5 days every second week for a total of 8 weeks followed by a 4-week observation period. Major side-effects of TNF-alpha therapy, seen in almost all patients studied, were fever and chills. As dose-limiting side-effects hypotension and liver toxicity were recorded in 4 of 5 patients treated with 200 micrograms/m2 twice a day. Pharmacokinetic studies revealed a TNF-alpha serum half-life of 13 to 25 min, a dose-dependent decrease in TNF clearance, and a dose-dependent increase in the area under the time/concentration curve. No anti-TNF-alpha antibodies could be detected, except in 1 patient. Tumour response to TNF treatment was poor. Only in 3 of 57 evaluable patients was partial tumour regression observed.