In this study, bighead carp treated with two doses, i.e. 400 and 580 μg MC-LReq (Microcystin-LR equivalent)/kg bw. After dosing bighead carp with 400 and 580 ug MC-LReq/Kg bw, the mean concentrations of microcystins (MCs) was significantly higher in boiled muscle than unboiled controls. These results indicate that the potential threat of microcystins contaminated fish to humans has been underestimated. The increase in microcystins occurs by the release of phosphatase-bound microcystins by boiling.