The protein requirement of young grey mullet, Mugil cephalus, was studied by using three diets containing 24%, 28% and 32% protein for eight weeks. The results showed that average weight gain and special growth rates(SGR) of the diet of 28% protein were both the highest. The protein content of the diets had no effects on the muscle composition of the fish. Four diets with protein to energy (P:E) ratios of 86. 2, 90. 3, 94.9 and 100. 0 mg protein/kCal energy were fed to groups of grey mullet for a period of six weeks.Average weight gains were 32. 5, 34. 2, 31. 3 and 23.8 g/ind respectively, and the SGR were 0. 70, 0. 79, 0. 74 and 0. 60 respectively. Composition of muscle was no significance affected by dietary P to E ratio. However, protein content of whole body decreased and lipid content increased at low P to E ratios. The optimum P to E ratio for grey mullet was determined to be 91mg/kCal, based on high weight gain and low lipid deposition in the abdominal cavity.