An effort was made to present the historical development of postmilking teat sanitizers, to discuss advantages and limitations of postmilking teat sanitization relative to specific mastitis pathogens, regulatory requirements, and the generic types of teat sanitizers. Methodologies used to evaluate the potential of teat sanitizers in reducing incidence of new IMI were discussed. Efficacy data from numerous controlled studies were discussed briefly. Teat-dip manufacturers advertise differences in efficacy values that were obtained under controlled research conditions. We are led to believe that relatively small differences in efficacy should prompt the use of one product over another. These efficacy differences have little comparative value, because the products, in most instances, were studied independently and the commercial extrapolations leave much to be desired for factual purposes. Management practices on individual dairy farms have more effect on reduction of rate of infections than do small differences in product efficacy. Also, some companies advertise about effective, in vitro germicidal activity. Such data do not relate to reduction in rate of udder infections and should not be considered evidence of efficacy in prevention of mastitis. A startling realization should become evident from this review; a paucity of information is available on some vital parameters relative to prevention of IMI. Many important areas of mastitis control related to postmilking teat antisepsis need an increased research commitment. Some of these areas include: effects of temperature on germicidal activity of teat dips; effects of climatic conditions on teat microflora; epidemiology of IMI with environmental pathogens; relationship between teat skin condition and incidence of IMI; and alternative control methods to reduce incidence of IMI. This question is asked often: "What is the best teat dip?" In my opinion, the best teat dip is the one that is dripping from teats when the cow leaves the parlor. In the words, most of the products sold today effectively prevent IMI when used properly.