Subchronic oral gavage toxicity of MCLR in water and in fish muscle was examined in male Balb/C mice for 13 weeks to assess the safety of aquatic products. The results showed that the liver coefficient (p < 0.05), the activities of ALT and AST (p < 0.01) increased significantly and distinct centrilobular to midzonal hepatucellular occurred after oral gavage of dissolved MCLR at a dose of 68.75 microg/kg (body weight), but neither influence on the activities of BUN and Cr nor histological changes on kidney were observed at any time point. In contrast, the administration of fish muscle-bound MCLR at the same dose resulted in no obvious subchronic toxicity in mice, except that the increase of liver coefficient (p < 0.05) and the activity of ALT (p < 0.01) can be observed only at the first week. It was concluded that the toxicity of fish muscle-bound MCLR was much lower than that of dissolved MCLR.