A 12-week growth experiment was conducted to quantify the optimum dietary pantothenic acid(PA)requirement of GIFT tilapia Oreochromis niloticus.Triplicate groups of experimental tilapia with initial body weight[(79.4±1.6)g]were cultured in 500 L aquaria(r=0.9 m,h=0.75 m;15 fish each aquarium)and fed with the experimental diets at six levels(0.5,4.8,9.5,18.2,36.3 and 74.4 mg/kg diet,respectively)of PA(supplied as Calcium d-PA).The results showed that,with the increasing of dietary PA level,weight gain rate of tilapia first increased linearly,then remained nearly unchanged at high PA treatments.Hepatic and muscle PA contents presented the same tendency with weight gain rate.Condition factor and hepatosomatic index first increased,then decreased with the increase of dietary PA level,and they were highest in 4.8 mg/kg PA supplement group.Whole body moisture content of tilapia first decreased,then increased as dietary PA increased,while whole body crude lipid content presented an opposite tendency.Hepatic total lipid concentration significantly decreased,the supplement groups showed significantly lower values than that in the un-supplemented group(P<0.05).The increase of dietary PA level also significantly increased serum high density lipoprotein cholesterol content(P<0.05).Broken-line regression analysis showed the optimum dietary PA requirement of GIFT tilapia was estimated to be 10.5 mg/kg for maximum growth,12.6 and 13.5 mg/kg for maximum hepatic and muscle PA concentration,respectively.