The fact that there are but few reports of serious accidents following the intravenous administration of mercupurin gives the impression that such reactions are very infrequent. Tyson1reported two deaths following the intravenous administration of mercurial diuretics (esidrone and mercupurin) to patients with nephrosis. She also cites other deaths in the literature from other mercurial diuretics. But we know of no reports of deaths following the use of mercupurin in patients with congestive heart failure. Each of us has given a large number of injections of mercurial diuretics during the past six or seven years to patients with congestive heart failure; our combined experience exceeds many thousands of injections, yet none of us had previously seen a serious or fatal reaction. It was with great surprise, therefore, that we learned that within a short space of time we had independently observed deaths immediately following the administration of mercupurin. A