The single ip LD 50 in mice was determined to be 65.7± 1.3mg/kg for CPT and 149.6±29.7 mg/kg for HCPT. The antitumor activity of HCPT was higher than that of CPT at the equi-toxic dose on the mice bearing ascites hepatorna,Ehrlich ascites carcinoma and ascites sarcoma 180. Both brugs could inhibit the syntheses of DNA and RNA. and inhibit transportation of thymidine and uridine into the hepatorna ascites cells in vitro. The therapeutic ratio of HCPT and CPT was 25 and 2.5 in mice bearing ascites hepatorna, ...