Post-milking teat disinfection is used to prevent new udder infections and to maintain healthy teat skin condition. Teat disinfection is most effi cacious against contagious bacteria, such as Staphylococcus aureus and Streptococcus agalactiae, but can have some effect also against environmental pathogens. The effect of the teat dips arises either from chemically active substances such as iodine or chlorhexidine, or from biocides such as fatty acids or lactic acid. In Finland, the active substance of teat dips is most often iodine or chlorhexidine. An effective teat dip prevents new udder infections, does not irritate the skin and is not toxic. In addition, teat dips should contain skin-conditioning components. No residues should remain in the milk and the active substance should not be absorbed into tissue. Teat dips must be registered by the EU authorities. In Finland, there are no legal requirements for effi cacy of teat dips, and evaluation of the effi cacy remains the user’s responsibility. The web site of the National Mastitis Council contains a review of scientifi c studies on the effi cacy of teat dips.