This plea for greater use of the opportunities which hospital control affords for the diagnosis and treatment of syphilis is based on replies to a questionnaire sent to institutions for the insane and mental defectives in U.S.A. and Canada, and on personal experience as superintendent of Dannemora State Hospital. At Dannemora, of syphilitic cases which received adequate treatment (limited by expense to 25 per cent.), with the exception of paretics, all responded by changes in the Wassermann reaction of blood and spinal fluid and by physical improvement, and nearly all by mental improvement, usually preceded by temporary loss of weight and occasionally by transitory mental exacerbations. Reports of four cases are given as examples. Treatment, the details of which are described, consisted in four courses of neo-arsphenamide given intravenously combined with mercury salicylate intramuscularly and sodium iodide by mouth, and with attention to diet and hygiene. Some paretics showed reductions in Wassermann, blood-count and globulin, but not in gold curve, nor has there, as yet, been a cure. General paralysis, however, is simulated by curable forms of neuro-syphilis. Syphilis may be a factor leading to loss of mental balance even without actual cerebral infection. A routine Wassermann test should be made on all inmates, and all serologically or clinically syphilitic should receive intensive treatment.