Feeding biology of Thryssa dussumieri and T. vitrirostris was studied for a period of one year (October, 1976 to September, 1977). T. dussumieri and T. vitrirostris are found to be carnivores with a preference for planktonic crustaceans in Parangipettai coastal waters. Polychaetes, molluscan larvae and juveniles of fish formed the supplementary food. Juveniles of both the species showed preference for Lucifer spp. and the adults mostly for Acetes spp., Lucifer spp., prawns, amphipod and crab larvae. No variation could be seen in the food of males and females in both the species. No seasonal variation in the food of adults of both species could also be noted. Percentage frequency of occurrence of ' actively fed ' stomachs showed an inverse relationship with gonadosomatic index and relative condition factor whereas empty stomachs showed a direct relationship with gonadosomatic index and relative condition factor. Feeding intensities in both the species were less during the peak breeding season, but were more during rest of the period particularly just after the spawning. Well developed gill rakers and the presence of minute teeth on vomer and palatines indicate that these two species are adapted to feed mainly on planktonic organisms.