An innovation often occurs in several arenas almost simultaneously, after being preceded by a long preparatory period when information and experience are accrued to the point at which opinion is influenced to change. Nevertheless, the introduction of an innovation is usually accompanied by resistance and hostility. This article traces the development of the concept and practice of antisepsis in health care, with emphasis on the contributions of three individuals who were contemporaries practicing in different health care fields, but who apparently were uninfluenced by each others' work. Semmelweis, a Hungarian obstetrician, recognized the importance of person-to-person transmission of infectious agents and effected dramatic reductions in puerperal mortality by requiring antiseptic handwashing. Lister, a Scottish surgeon, was the first physician to apply the germ theory to clinical practice and developed the techniques of antiseptic surgery and wound care, resulting in dramatic reductions in surgical mortality. Nightingale, a British nurse, initiated sanitary reforms in hospitals, schools, and military camps in England and abroad, incorporating high levels of environmental and personal hygiene. These reforms were also succeeded by dramatic reductions in mortality. In light of historical and current evidence of efficacy and the evidence of continued inadequacies in practice, it seems reasonable to speculate that further reductions in nosocomial infection rates are possible by a more careful application among individual practitioners of the basic principles of antisepsis.