The diagnostic reliability of techniques for determining the prevalence of teat canal infections varies: bacteriological results obtained by examination of teat canal swabs were 20% higher on average than those of foremilk samples (FMS) examined and classified according to the criteria of the International Dairy Federation (IDF). Since they are based exclusively on the bacterio-cytological results of the FMS, the IDF criteria for the classification of the various forms of subclinical udder conditions do not permit an accurate classification of the health status of the udder.