Abstract: A 60d growth trial was conducted to investigate the effect of dietary supplemental glutathione (GSH) on the toxicity of microsystins from oral administration of cyanobacteria on yellow catfish.Six isonitrogenous (45% crude protein) and isocaloric (19.5 kJ/g gross energy) experimental diets were formulated.Cyanobacteria free and GSH free diet was used as the positive control.Another five diets were formulated to contain 7.5% algae meal (dietary microcystins were about 58 μg/g) supplemented with GSH at 0 (Negative control),200,500,800 and 1400 mg GSH/kg diet respectively.During the first 30 days,there was no significant difference in feeding rate (FR) between the fish fed negative control and positive control (P>0.05).During the second 30 days,yellow catfish fed negative control had higher FR than the fish fed positive control and all GSH containing diets (P0.05),and all fish fed GSH containing diets had lower renal GSH than fish fed the positive control (P<0.05),but all fish fed GSH containing diets had higher renal GSH than fish fed the negative control (P<0.05).Liver and muscle MDA contents of the fish fed with 200,500 and 800 mg GSH/kg diet were significantly lower than that of the negative control (P<0.05).During the whole experimental period,microcystins (MCs) accumulated in fish liver,kidney,and intestines first decreased with dietary GSH (P<0.05) and then reached a stable level at 500 and 800 mg GSH/kg supplementation level,and finally increased at 1400 mg GSH/kg supplementation level.Based on weight gain,liver and muscle MDA contents and tissues MCs concentration,it suggested dietary 500-800 mg GSH/kg supplementation could be helpful to reduce the toxicity of MCs on yellow catfish.