A phase I and pharmacokinetic study of recombinant tumor necrosis factor (rH-TNF Asahi) was carried out in 29 patients, who received a total of 72 courses with doses ranging from 1 to 48 X 10(4) units/m2. Drug was given as 1-h i.v. infusions. Acute toxicities, taking the form of fever, chills, tachycardia, hypertension, peripheral cyanosis, nausea and vomiting, headache, chest tightness, low back pain, diarrhea and shortness of breath were seen, but were not dose-limiting or dose-related. Some early rise in SGOT, without any change in serum bilirubin, was noted at the highest doses. Eosinophilia, monocytosis, mild hypocalcemia and an increase in fibrin degradation products were seen in a few patients. The dose-limiting toxicity was hypotension, which occurred after the end of the drug infusion and was seen in all 5 patients treated at the highest dose. There was no mortality or long-term morbidity. There were no responses. Pharmacokinetic studies indicated a rapid plasma clearance and a short plasma half-life, generally less than 0.5 h.