Abstract: In this paper, the effects of Antibiotic 1588 on different kinds of animal transplantable carcinoma and sarcoma are reported.The inhibition rates of Antibiotic 1588 were 90%, 85.4% 83.1%, and 50.6% in the treatment of S 180, U 14, Lio-1 and B 22, respectively, after intraperitoneal injection for 10 days at the daily dosage of 12.5 mg/kg. The survival periods were 27%, 43%, and 48% longer than control animals in the ascite form of EC, ARS and HCA at the daily dosage of 12.5 mg/kg for 10 days. For Walker-256 (ascite form) it showed a longer survival time (118% of control animal)at the dosage of 6.25 mg/kg for 6 days and 86% at the dosage of 3.1 mg/kg for 6 days. Antibiotic 1588 showed no effect on L₆₁₅ leukaemia in mice. The LD₅₀ in S180 was 2.042+0.497mg/kg (P=0.95).In the case of S180, Antibiotic 1588 was given at different days after inoculation of cancer cells. The inhibition rate was higher when 1588 was given earlier, Furthermore, there was not much difference in the inhibition rate whether the drug was administrated in one dose or divided into several doses.The antitumor effects of two main components of antibiotic 1588, 1588-74-3 and 1588-74-9 were compared. When they were injected at the dosage of 3 mg/kg for 10 days intraperitoneally, the inhibition rates of S180 (solid form) were 89.0% and 85.2%, respectively. In comparison the inhibition rate of bleomycin A₅ in the same experiment was 84.9%.