A n experiment was conducted on 16 floating cages, each of a total water volume of lm 3 stocked with Nile tilapia ftngerlings weighing 30.67 to 30.22 g at the experimental start.The 16 cages represented four stocking densities (80 Dl; 100 D2; 120 »3 and 140 D4 fiih/m 3 ) and four protein levels within each density tested (PI 20 ; P2 24 ; P3 28 and P4 32%). The experiment lasted 6 months after start. Results obtained are summarized in the following: (1) Increasing the protein level within each stocking density increased significantly (P<0.05) both body weights and length of fish. (2) Wilhin each protein level tested, increasing the stocking demky resulted in significant decreases in body weight and length of Nile tilapia (3) Both protein levels and stocking densities released significant effects on gains in live weights, specific growth rate, feed conversion ratio and protein efficiency ratio. The total cage yield differed among the 96 Nabil F. Abdet-Hakim and El-Saied T. Moustafa where fish at a density of 120 fish/m 3 fed on the diet with 32% protein gave the highest yield of marketable size fish,