Clarias gariepinus as one of the main freshwater fishes was reared in concrete ponds at three initial sizes and three stocking rates. In the first experiment, three concrete ponds were stocked with the same initial fish size of about 189 g at three stocking densities of 5, 8 and 10 fish/m , while in the second experiment, three size groups ranging from 90 to 120 g, from 170 to 200 g and larger than 200 g of Clarias gariepinus were reared in three ponds (one pond for each size) at stocking rate of 5 fish/m for 95 days. Ponds were supplied with underground water which was partially drained every day. Fishes were fed with supplementary feed containing 32% protein at 3% of body weight 6 times a week. Results showed that C. gariepinus weight increased from about 189g to 427.3, 352.4 and 295.03g in ponds stocked with 5, 8 and 10 fish/m respectively. Present results showed also that weight gain (g), average daily gain (g/fish/day) and the specific growth rate decreased with increasing stocking density. Gain in body weight and the average daily gain of C. gariepinus increased with increasing initial weight, while specific growth rate decreased with the increase in initial body weight. Economically, results indicated that C gariepinus weighed 170 to 200g at stocking rate of 5 fish/in3 could be considered as the best size and stocking rate for rearing them intensively in concrete ponds.