The results of the experiments conducted during 1980-82 on the monoculture of milkfish at Marine Fish-farm, Mandapam are presented. In a 0.25 ha earthen pond, each experiment was conducted for a period of 10 months. Fertilization with 1000 kg/ha of chicken manure and 400 kg/ha of N-P-K (12-24-12) was done in the first experiment. Supplementary feed at the rate of 5-10% body weight of the fish was given in the second experiment. The stocking density of 4000 fingerlings/ha yielded 216 kg/ha in the fertilized pond with a survival rate of 89.7% and 852 kg/ha in the unfertilized pond with 63% of survival.