Abstract: Using a unique data set comprised of original research of both the corporate Web sites of the Big Four—PwC, Deloitte, KPMG, and EY—and their affiliated law firms, as well as archival material from the legal and accountancy press, this article documents the rise and transformation of the Big Four legal service lines since the enactment of the Sarbanes Oxley Act of 2002. Moreover, it demonstrates that there are good reasons to believe that these sophisticated players will be even more successful in penetrating the corporate legal services market in the decades to come, as that market increasingly matures in a direction that favors the integration of law into a wider category of business solutions that these globally integrated multidisciplinary practices now champion. We conclude with some preliminary observations about the implications of the reemergence of the Big Four legal networks for the legal profession.