The stomachs of 11,766 king mackerel caught between June 1977 and November 1981 from seven areas (North and South Carolina, Georgia, east central Florida, south Florida, northwest Florida, Louisiana, and Texas) were examined. Forty-one percent of the stomachs were empty. The percent volume of fish in non-empty stomachs ranged from 84.9% in northwest Florida to 99.6% in Louisiana. The percent frequency of occurrence of fish ranged from 77.5% in south Florida to 99.1% in Texas. Thirty-one fish families were contained in the diet. Clupeidae, the dominant family, was present in stomachs from all seven areas. Other families of importance were Carangidae, Sciaenidae, Engraulidae, Trichiuridae, Exocoetidae, and Scombridae. Decapterus punctatus was the most important fish species in Georgia and northwest Florida, whereas in each of the other five areas, a different species was most important: Brevoortia sp. in North and South Carolina, Sardinella aurita in east central Florida, Hemiramphus brasiliensis in south Florida, Cynoscion arenarius in Louisiana, an Trichiurus lepturus in Texas. Lengths of the four most abundant prey species exhibited little variation with the sizes of king mackerel. Squid was the dominant invertebrate in the stomachs from North and South Carolina, Georgia, east central Florida, and northwest Florida, while penaeid shrimp was dominant in south Florida and Texas. King mackerel were primarily piscivorous; they fed heavily on schooling fishes in all seven areas.