The pioneer work of Chargin, Leifer, Hyman and their associates1 with the five day intravenous drip has stimulated a large number of clinical studies on other intensive methods of antisyphilitic treatment.2 The duration of treatment has been varied from one day to twenty weeks, the frequency of injections has been varied from twice daily to twice weekly, and in some clinics artificially induced fever has been used as an adjunct to the intensified course of arsenotherapy. As with any chemotherapeutic procedure, the three major considerations which determine the utility of these treatment schemes are their therapeutic efficacy, their toxicity and their practicability. Recent studies in experimental rabbit syphilis provide a helpful orientation to the first two of these points. The total curative dose of mapharsen was found to be more or less constant, largely independent either of the frequency of injections or of the duration of treatment.3