The geographic range of the Timber Rattlesnake (Crotalus horridus) encompasses most of the eastern half of the United States. Although the overall diet composition of C. horridus has been well documented and has been reported to be very broad, local population variation has not been studied. We examined the diet and foraging behavior of C. horridus from four separate populations in Pennsylvania and New Jersey. A total of 253 prey items from scat samples, stomach samples, and field observation were identified to species or family level. Although voles (Myodes gapperi) and mice (Peromyscus spp.) comprised the bulk of the diet in all populations, relative prey species frequency differed significantly among the four populations. These data indicate that the food habits of C. horridus varied widely even within relatively small geographic distances. Comparisons with small mammal trapping data further suggest that the diet composition of this ambush predator may not simply reflect the availability of prey species. Radiotelemetric observations of C. horridus further indicate differing frequencies of log-oriented foraging behavior among the study sites. Analysis of body posture revealed an alternative ambush foraging posture (non-log-oriented posture) which also exhibited variation in frequency among study sites. However, selected foraging habitats at all study sites were typified by a locally high density of fallen logs and other woody debris (6% of forest-floor cover/m²). These findings indicate geographic variation in the foraging ecology of C. horridus and suggest behavioral plasticity in foraging response to available prey.