This paper estimates the effect of Wal-Mart expansion on wages, benefits, and skill-composition of retail workers during the 1990s. We exploit the spatial pattern of Wal-Mart diffusion, radiating outward from the original store in Benton county, Arkansas, to control for potential endogeneity in store openings using both instrumental variable and control function approaches. Estimates from state and county level data suggest that store openings reduced both the average earnings and health benefits of retail workers. At the county level, a new Wal-Mart is found to reduce retail earnings, on average, by .5 to .9 percent. Moreover, we find that changes in skill-composition explain only a small part of compensation reduction, indicating that the decline in retail wages reflect a reduction in labor market rents.