The aim of the study was to assess the effects of orally applied praziquantel on the treatment efficacy against most abundant tapeworms (Atractolytocestus huronensis Anthony, 1958 and Khawia sinensis Hsü, 1935) of common carp (Cyprinus carpio Linnaeus). Naturally infected fish (one-year-old; K1+) were divided into 3 trial groups containing 17 specimens and administered with praziquantel mixed in heat-treated amyloid vehicle (in doses of 50 mg.kg-1 body weight). In 3 groups of control, the fish were administered amyloid vehicle only. Fish were examined by using of gut dissection 2, 4 and 6 days after administration. At 48 hours post-treatment, significantly lower prevalence of both parasites was found. The invasion of A.huronensis was fully eliminated in all fish after 96 hours whereas some specimens of K.sinensis still persisted in the gut of few fish. The full elimination of both parasites was observed 6 days after administration. Our results showed that elimination of K. sinensis takes longer than elimination of A.huronensis. The dose of 50 mg kg-1 of orally applied praziquantel is effectual to control A.huronensis and K sinensis infections in common carp successfully. The effect of oral applied praziquantel on the hematology and biochemical parameters blood of common carp (Cyprinus carpio L.), infected by the tapeworms Atractolytocestus huronensis and Khawia sinensis was the object of analyse. It was the partial goal of the work. The infected fishes were divided to the six groups. The praziquantel was applied stirred in amyloid vehicle in dose 30 mg/kg of quick materiality for two groups and for two to other groups in dose 50mg/kg of quick materiality. Only clean amyloid vehiculum was applied to two control groups. Blood taking and resulting patoanatomic investigation was effected 24 and 96 hours after application of praziquantel. Results of hematology investigation of blood obtained 24 hours after the application point on significant fall (p< 0,01) of the number of erythrocytes, hemoglobin and hematocrit in both groups E1 and E3, which achieved the original surface after 96 hours. The significant upsurge (p<0,05) of the surface serum hepatic enzyme ALT was recorded after 96 hours.