We compared age- and sex-class structure between two populations of eastern chipmunks (Tamias striatus) occupying study plots within uncut (reference) and managed (fragmented) forest sectors in central Pennsylvania from 1992–1995. In addition, we compared reproductive condition, weight and length of time chipmunks remained on study plots between the two populations. There was no difference (P > 0.05) in age class, sex class or reproductive condition between the populations occupying each sector. Chipmunks remained on plots in both uncut and managed forest sectors for an average of 2.2 and 2.3 mo, respectively. Weights of individual chipmunks did not differ (P > 0.05) between the two populations and averaged 81.5 g. Chipmunks in both populations, however, weighed significantly (P ≤ 0.05) less in 1993 following a poor acorn crop in 1992 than in other years. Although eastern chipmunks primarily inhabit mature eastern deciduous forests, fragmentation had no apparent influence on the demography of populations of this sciurid.