Smallmouth bass (Micropterus dolomieu) introduced nearly 50 years ago have established a permanent population in Little Moose Lake, NY. Over 500 smallmouth bass were collected by angling in the littoral zone from June to August. Gut contents were compared for differences based on length of bass, date of capture, and substrate type where each fish was caught. Crayfish were the most frequent diet item and made up the largest percent composition by number. The average number of crayfish per stomach increased with bass length as did the number of fish per stomach. Crayfish, Ephemeroptera, Odonata, and fish made up 77% of the total number of diet items, excluding zooplankton. A noticeable diet shift from smaller diet items (Ephemeroptera) to larger ones (crayfish and fish) occurred when smallmouth bass approached 150 mm. A high amount of diet overlap occurred between bass caught over different substrate types and among most size classes. Smallmouth bass in Little Moose Lake were opportunistic feeders, using benthic, terrestrial, and pelagic littoral zone food resources. The most likely processes by which smallmouth bass affect salmonid and native fishes in Little Moose Lake are competition for food resources and predation.