Geoffroy's cat (Oncifelis geoffroyi) is a little-known South American felid. We report here the first detailed data on its food habits and variations among 3 areas of the Argentine Pampas grassland. Analysis of 421 scat samples showed a relatively narrow trophic niche, dominated by vertebrates, especially small rodents. Despite a wide overlap in diet composition, geographical variation was found in frequency of occurrence of primary food categories, presence of secondary food items, and mean weight of vertebrate prey. These differences seem to be related to variation in food availability and suggest that Geoffroy's cats are able to show a certain degree of adaptability in foraging behavior.