We examined the antitumor effect of recombinant human lymphotoxin (rHuLT) on a xenotransplantable human malignant glioma line. Tumor-bearing nude mice were treated with rHuLT for three weeks following four schedules: intratumoral injection of rHuLT 20,000 units once a week, twice a week, intravenous injection once a week and twice a week. The inhibition rate of tumor growth was 98.8%, 99.1 %, 92.1 % and 98.8%, respectively. Histologically, necrotic lesions were observed in the tumors of all treated mice. Thrombo-obstructive changes of tumor vessels were also seen in the tumors of mice after intravenous injection of rHuLT. None of the mice died as a result of this treatment in spite of significant body weight loss. These results indicate that rHuLT has a strong antitumor effect on a xenotransplantable human malignant glioma line.