Robert J. Alexander (1918–2010), a pioneering Latin American specialist, who focused much of his scholarship on the governmental systems, political parties, leaders and labor movements of Mexico, Central America and South America, is also known for his collection of an estimated 10,000–12,000 Latin American/Caribbean interviews amassed from the late 1940s to the turn of the twenty-first century. During this same 50-year period, Alexander, who also possessed a strong interest in U.S. radicalism, assembled a smaller interview collection of U.S. left-wing activists that include those involved in Lovestoneite, Trotskyist, Shachtmanite, etc. organizations. In addition to his voluminous writings on Latin America, Alexander also devoted significant energy during the last three decades of his life to writing the history of dissident communist movements (i.e., the Communist Right Opposition, Trotskyism, and Maoism) throughout the world. The purpose of this article is to discuss and analyze Alexander's collection of interviews of U.S. political and labor radicals while critically examining his major works on dissident communism. In spite of the contributions he has made in these fields, I conclude that there are serious methodological flaws with Alexander's writings on dissident communism although his U.S. left-wing interview collection of political and labor radicals is invaluable for the study of the twentieth-century U.S. radicalism.