We examine the competition among Big 4 firms for Andersen’s public clients during and after its demise in 2002. Andersen’s failure provides a quasi laboratory to investigate how audit firms compete for new clients. Our analysis focuses primarily on the acquisition by Big 4 firms of some, but not all, of Andersen’s individual offices in the United States, and the resulting impact on public clients. The United States Congress expressed concern about the failure of Andersen when it required the GAO to study the competitive nature of audit markets as part of the Sarbanes Oxley Act (GAO 2003). We build on the original GAO study by incorporating office purchases into the analysis of competition for Andersen’s public clients. We use news reports to construct a database that differentiates between Andersen offices that were effectively purchased or not purchased by the surviving Big 4 firms.1 This database enables us to explore the factors associated with Big 4 office purchases, differences in strategies used to acquire Andersen’s clients, and the impact of these different acquisition strategies on audit fees. We identify 65 Andersen offices that served public clients in 2001. Big 4 firms purchased 39 offices and three local industry practice units from large offices. Based on these data, we consider four types of Andersen client switches: (a) EARLY_SWITCHERS: clients who switched prior to the purchase of their Andersen office, or if the office was not purchased, prior to the first Andersen