This study provides a detailed, in-depth analysis of a single incident rooted in the effort of a group of professional employees to serve the public welfare. It reveals in microcosm the interplay of political forces, economic interests, personal ambition, organizational structure, and professional ethics that culminated in an act of whistle-blowing. The incident took place during the final construction phase of the Bay Area Rapid Transit System (BART), designed to be America’s first attempt at space-age mass transportation. Three BART engineers, convinced of the lack of responsiveness of management to their concerns about the system’s safety, were fired for insubordination and other organizational sins. Based upon repeated interviews with the engineers, with BART managers and directors, and with the professional societies involved, as well as upon an extensive body of documents and court depositions, legislative reports, media reports, and institutional memoranda. Divided Loyalties sets a theoretical context for the issues, traces the incident from its beginning, examines the aftermath of the engineers’ dismissal, and concludes with a set of recommendations that should be considered by public and private organizations, professional associations, agencies of government, and individual professional employees.