The concurrent sentence doctrine is a judicially-created rule of criminal procedure. In this article, Professor Emanuel traces the history of the doctrine from its roots in eighteenth-century England to its current status in state and federal courts. Recently, the United States Supreme Court effectively forestalled the use of the doctrine in any federal felony conviction; however, Professor Emanuel argues that the doctrine remains viable in collateral actions for postconviction relief from federal convictions and in state couts.