Abstract: The toxicity of prothiomide(PTH)+rifam-picin(RFP)+Dapsoae and PTH+isobutylpiperaziayl rifamycin(R₇₆₁)+Dapsone(treatment groups)in the treatment of multibacillarp leprosy were compared with the corresponding control groups that did not include PTH. The duration of treatment was 6 months. The results showed that the toxicity of the treatment groups with PTH increared remarkably, and was different significantly in comparing with the corresponding control groups without PTH. The main toxic side effect was liver damage. One.patient died of acute yellow atrophy of the liver in the treatment group(PTH-E-RFP+Dapsoae)at the end of 6 months of treatment. The results indicated that the increase of toxicity of the treatment groups was related to PTH. So, PTH in combination with RFP(or R₇₆₁)and Dapsone should not be recommended for the treatment of multibacillarp leprosy in our country.