Few wildlife studies have addressed the impacts of ski-run development. Ski-run development appears similar to disturbance caused by clearcuttting (e.g., increased fragmentation and edge habitats), although the processes of creating ski runs and ongoing disturbance from maintenance and snow compaction are different. We compared small-mammal density and survival on 2 ski runs (>30 yr old) paired with forested sites at Vail ski area, Colorado, USA. Using Pollock's robust design, we live-trapped small mammals during 4 summers (1998–2001). We captured 771 individuals 1,751 times in 19,000 trap-nights. Based on abundance estimates from program CAPTURE, ski runs had lower densities of red-backed voles (Clethrionomys gapperi), which were captured only in forest edges of ski runs, and higher densities of deer mice (Peromyscus maniculatus) and least chipmunks (Tamias minimus) than adjacent forest sites. Based on survival estimates from program MARK, survival of red-backed voles (averaged over the 4 years of our study) was greater in forested edges of ski runs than forested sites. Too few recaptures occurred for survival estimation of deer mice and least chipmunks on forested sites, confirming their lack of preference for closed-canopy forests. Changes in small-mammal proportions likely occur as a result of ski-area development, and how these changes influence other species (e.g., through food-web dynamics) needs to be considered when managing ski areas.