Between 1916 and 1955 the Mayo Clinic became recognized as one of the premier institutions specializing in the treatment of syphilis. First under the direction of John H. Stokes (1916-1924) and later Paul A. O'Leary (1924-1953), its Department of Dermatology and Syphilology, together with the members of the Clinical Cooperative Study Group, oversaw the establishment of standardized methods for the administration of the existing arsenicals and the introduction of new therapies. Malaria therapy, heat therapy, penicillin, and oxytetracycline each represented important advances in the treatment of syphilis and were extensively evaluated. Two important ancillary benefits of syphilis treatment were the development of routine intravenous techniques, which would later prove invaluable for the administration of antibiotics and cancer drugs, and the establishment of large cooperative clinical trials, the first of their kind. Under the leadership of Stokes and O'Leary the department produced a stream of pivotal clinical research that contributed to the effective management of syphilis in the United States.