Stomach contents of 10 fish species were examined to evaluate several scales of spatiotemporal variation foraging success within an Illinois stream. Most species fed primarily on aquatic or terrestrial invertebrates, but one species specialized on fine detritus. Fish are a wide variety of invertebrate taxa, and diet overlap based on prey taxa was extensive among fish species and age classes. Foraging success, measured by number and size of prey eaten, varied among seasons, years, substrate composition and amounts of woody debris. However, no factor influenced foraging success of all species, and no 2 species responded identically to all factors. Fish generally fed most successfully in June, and least successfully in Oct. Some fish ate more or larger prey in a study area with gravel-cobble substrates than in a silt-sand area, and many ate more or larger prey in sites with woody debris than in sites from which debris was removed.