This study was performed to investigate detoxifying enzyme activities of carboxylesterase(CE), glutathione S-transferase(GST) and lactate dehydrogenase(LDH) at variable toxicity levels in fresh water fish, carp(Cyprinus carpio L.). The carp was exposed to single and combined pesticides of IBP, isoprothiolane and cartap for 48 hr at sublethal doses, LC_(10) and LC_(26). The detoxifying enzyme activities were assayed for the liver, head and gut of the carp. The enzyme activities we discovered were as follows: Both activities of CE and GST were increased at the sublethal doses but were declined by increasing doses. In the gut, we found that the CE activity had high levels in the treatment groups of isoprothiolane+IBP and isoprothiolane+cartap. In the head, the CE activity had high levels in the treatment groups of cartap, IBP and isoprothiolane. However, the GST activities were inconsistent in the head and gut of the fish. Also, the GST activity was declined by increasing protein contents. The highest LDH activity was shown in the isoprothiolane treated fish, while the lowest activity was observed in the isoprothiolane+cartap treatment.