On examination of the correspondence among the principals involved, as well as the original patent application being prepared by Morton, it has become possible to reconstruct some of the remarkable details attending the first use of ether anesthesia at the Massachusetts General Hos pital in the autumn of 1846. At the time that Warren invited Morton to demonstrate the use of his "ethereal vapor" for anesthesia in a minor operation on Oct. 16, 1846, the exact chemical composition of the agent used was being held secret by Morton; Warren was clearly disturbed by this unethical use of a secret "nostrum." When the time arrived 3 weeks later for its possible use for a serious "capital" operation, Warren employed a simple stratagem of public confrontation to discover from Morton the true nature of the substance to be used. On being informed that it was pure unadulterated sulfuric ether, not some mysterious new discovery labeled "Letheon," Warren gave approval for its first use in a "capital" operation (low thigh amputation) on Nov. 7, 1846. Despite this revelation to the immediate participants, a veil of secrecy continued to surround the substance for many months, an anomalous situation evidently traceable to Morton's desire for personal reward from the discovery. It was this matter of secrecy, rather than priority for its discovery, that surrounded the early use of ether anesthesia with controversy and recrimination both in this country and abroad.