This research is supported by a grant from the Social Sciences and Humanities Council of Canada. For comments that greatly improved our work we are grateful to Don Palmer, three particularly astute and exceptionally helpful ASQ reviewers, Harry Barkema, Henrich Greve, Olav Sorenson, and workshop participants at CentER-Tilburg University, CKIR-Helsinki School of Economics and Business Administration, and Northwestern University. We also thank Whitney Berta, Jackie Hick, and Leisa Sargent for assistance with data collection and coding.We examine acquisitions by multiunit chain organizations to determine why they acquire a particular target rather than others that are available to them and thus better understand chain growth. We advance experiential and vicarious learning processes as an explanation for chains' next spatial move. Our analysis of Ontario nursing home chains' acquisition location choices from 1971 to 1996 provides broad support for a learning perspective, demonstrating how experiential and vicarious processes shape and constrain the locations of chains' acquisitions. Experiential processes lead chains to replicate themselves by acquiring components geographically and organizationally similar to their own most recent and most similar prior acquisitions and their own current components. Vicarious processes lead chains to imitate location choices of other visible and comparable chains' most recent acquisitions, prior acquisitions nearest to potential targets, and their current components. Our study thus establishes organizational learning as a conceptual foundation for predicting the location of a chain's next acquisition and, more generally, the spatial expansion of chains over time.-Although the chain organizational form arguably rivals the Mform as the twentieth century's most successful organizational form, organization theorists have only recently begun to study them systematically (e.g., Darr, Argote, and Epple, 1995; Ingram, 1996a, 1996b; Bradach, 1997). And although the chain form renders physical space a conspicuous variable, thus far, little attention has been given to the dynamics of chains' spatial expansion (Usher, 1995; Greve, 2000; Ingram and Baum, 1997a, 1997b, 2001). Yet chains' growth and spatial expansion patterns are inherently interesting and important from both organizational and societal perspectives. Chains are collections of service organizations, doing essentially the same thing, linked together into larger super-organizations (Ingram and Baum, 1997a). Often, geographic location is the only difference among a chain's components. Location is thus a critical strategic and organizational variable for chains. More generally, the spatial expansion of chains underlies the rise of an organizational form that is coming to dominate every service industry at the same time that service industries are becoming increasingly important to economies around the world.To date, research on chains' spatial expansion has been left primarily to economic geographers, who have produced an extensive cas...