Microstegium vimineum (Japanese Stiltgrass) is an invasive, annual C4 grass that frequently forms dense populations along roads in the eastern US. We examined data from a survey that included 768 forested sites in western North Carolina, and carried out a transplant experiment to test (1) if the distribution of Japanese Stiltgrass is associated with roads and (2) if roadsides differ from forest interiors in terms of the frequency, abundance, and individual vigor of the species. Japanese Stiltgrass abundance was positively associated with total road length within watersheds. The species was much more common and abundant on roadsides than in forest interiors. Greenhouse-established individuals of Japanese Stiltgrass that we transplanted onto roadsides grew larger than those we transplanted in forest interiors. The 2 groups had similar survival rates. Our results suggest that roads promote the spread of Japanese Stiltgrass and that individuals and populations are more robust on roadsides than in forest interiors. However, the species can grow in forest interiors, suggesting its lower abundance and size there may result from limitations in dispersal, germination, or resource acquisition.