The proclamation, “Gentlemen! this is no humbug,” attributed to John Collins Warren, M.D., was not identified in any contemporaneous eyewitness report of William T. G. Morton’s October 16, 1846, demonstration of ether at Massachusetts General Hospital. The earliest known documentation of the proclamation is in Nathan P. Rice’s biography of Morton, first published in 1859. Only three eyewitnesses, Washington Ayer, M.D., Robert Thompson Davis, M.D., and Isaac Francis Galloupe, M.D., reported Warren’s alleged proclamation. However, their accounts first appeared in 1896, 50 yr after Morton’s demonstration of etherization. Although Warren’s alleged proclamation appears plausible, the overall impression from eyewitness statements and publications relating to the October 16, 1846, demonstration of etherization is that it may not have been made.