The Yamasaki-designed Pruitt-Igoe high-rise public housing project in St. Louis was at the heart of one of the greatest tragedies in the history of American housing. Initially praised for its design innovation, it proved to be a failure, with destitution, crime, and vandalism leading to its ultimate demolition. In the debate that continues over the causes of the calamity, the responsibility of Yamasaki – and the power or weakness of modern design itself – is at issue. After presenting Yamasaki’s contributions to the debate over public housing strategies, this chapter reviews the status of the scholarly investigation over what went wrong in Pruitt-Igoe, and specifically, the question as to what role architectural design played in its failure.