The diet of cod (Gadus morhua L.) in the Celtic Sea was studied by analysis of stomach contents. Cod were found to prey on decapods (43% of weight) and fish (54%). Cod are opportunists and the diversity of food composition reflected the dispersal of prey according to season and area. The Norway lobster (Nephrops norvegicus) is eaten chiefly in the central area; Brachyura are more numerous off the Irish coasts. The most abundant fish prey are Norway pout (Trisopterus esmarki), poor cod (Trisopterus minutus) and blue whiting (Micromesistius poutassou).