On the eve of the First World War, two iconoclastic young journalists, H. L. Mencken and George Jean Nathan, were offered the co-editorship of The Smart Set, a New-York based magazine with literary ambitions. During their nine years as co-editors, from 1914 until 1923, Mencken and Nathan transformed The Smart Set into a must-read of the early jazz era, established themselves as two of America's foremost critics, and became bona-fide celebrities in American popular culture. Indeed, "Mencken and Nathan" were at times as popular collectively as they were separately. Among their writings in The Smart Set are a jointly authored series of nine "Conversations," written dialogues between Mencken and Nathan that depict their personal interactions in various circumstances and locales, chronicling a series of events perhaps both real and imagined. Taken together, the "Conversations" offer a plausible if somewhat exaggerated representation of their idiosyncratic relationship as authors and editors. Published here with a new Introduction and Glossary, The Smart Set "Conversations" of H. L. Mencken and George Jean Nathan are reprinted in the present edition in their entirety. H. L. Mencken and George Jean Nathan were controversial figures during their era. They were culture warriors, disruptors, instigators, masters of satire and irony. Their writings were often offensive to readers then and will likely engender only greater offense now. Contemporary readers may find The Smart Set "Conversations" to be a timely reflection upon the history of the American public dialog. This edition of The Smart Set "Conversations" is intended for mature readers interested in the history of arts and literature, as well as the American popular culture of the 1920s.