What happened to the Hohokam? This issue of Archaeology Southwest explores initial results of the Center’s long-term research on the dramatic population decline that occurred in the southern Southwest almost a century before the arrival of the Spaniards. Contributors discuss the impact of migration on demographic change, as well as the methodologies they employ to address this complex research problem. Patterns are described for each of five study areas: the lower Salt River Valley, Perry Mesa, the lower San Pedro Valley, the Tonto Basin, and the Safford Basin. The issue closes with a summary of preliminary conclusions and ongoing avenues of inquiry.