This paper studies interplant sex segregation in the U.S. manufacturing industry. The study differs from previous work in that we have detailed information on the characteristics of both workers and firms, and because we measure segregation in a new and better way. We report three main findings. First, there is a substantial amount of interplant sex segregation in the U.S. manufacturing industry, although segregation is far from complete. Second, we find that female managers tend to work in the same plants as female supervisees, even once we control for other plant characteristics. And finally, we find that interplant segregation can account for a substantial fraction of the male/female wage gap in the manufacturing industry, particularly among blue-collar workers.