Following the administration of carbon tetrachloride to rats, the liver conjugase level decreased with 4 hours and continued to be low till 24 hours. Plasma conjugase did not change till 6 hours after administration, but at 24 hours showed a significant increase. Histological examination of the livers revealed liver damage even by 6 hours following carbon tetrachloride administration. However, centrilobular liver cell necrosis could be seen only in the livers of animals killed after 24 hours following carbon tetrachloride administration. The properties of plasma and liver conjugases were similar. The pH optimum of the conjugase in the plasma obtained at 24 hours after carbon tetrachloride administration was 4.5 which is the same as that of the liver conjugase and the Km values were also almost the same. Both the enzymes were stimulated by thiol compounds. The inverse relationship between liver and plasma conjugase activities following carbon tetrachloride administration suggested that liver is probably the source of plasma conjugase.