Abstract: Effects of praziquantel on monoamines and their metabolite contents were studied using HPLC-electrochemical detector. Praziquantel was found to increase the acidic metabolites of dopamine, DOPAC and HVA, and of 5-HT and 5-HIAA levels in the striatum and limbic areas. The increase in DOPAC and HVA reached their peaks 0.5～1 h after a dose of 500 mg/kg in the two regions, while the dopamine and noradrenaline levels were unchanged. The elevation of DOPAC, HVA and 5-HIAA was in dose-dependent manner. When higher dose of praziquantel (1000 mg/kg) was given, the values of dopamine in the striatum and of noradrenaline in the limbic area were lowered. The results show that the turnover rates of dopamine and 5-HT were increased.