Objective: The teat canal of lactating dairy cattle is the first barrier against mastitis pathogens invading the teat cistern and the udder lumen. However, in several studies it could be shown that the teat skin and the teat canal epithelium are colonized by mainly staphylococci as well as by other pathogenic or facultative pathogenic micro-organisms. The aim of the study was to evaluate the pathogen pressure on the bovine mammary gland and to establish data on the prevalence of relevant micro-organisms. Material and methods: In 32 randomly selected German dairy farms the colonization of the teat skin and the teat canal by S. aureus (Baird Parker agar), Sc. uberis (modified Rambach agar according to Watts et al. [1993]), enterococci (kanamycin esculin azide agar) and coliforms (ChromoCult Coliform agar) was investigated by the wet/dry swab technique DIN 10113-1: 1997-07. Results: In total 84.5% of all 1358 investigated teat canals of clinically healthy cattle were colonized by at least one of the four pathogen groups. S. aureus was isolated from 72.2% of the teat canals. For S. aureus, Sc. uberis and E. coli maximum bacterial counts of > 10 ⁶ cfu/swab and for other coli-form bacteria > 10 ⁷ cfu/swab were detected. Correlations could be found between the bacterial counts on the teat skin and in the teat canal within the pathogen groups S. aureus, Sc. uberis, E. coli and other coliforms (Spearman's rank correlation coefficient r ≥ 0.30, p < 0.001) as well as between the environmental udder pathogens Sc. uberis and coliforms (r ≥ 0.25, p < 0.01). Conclusion and clinical relevance: The variation of the bacterial counts on teat epithelia could be an indicator that the microflora of the teat canal epithelium can be affected by management practices in dairy farms. The results of this study point out that under field conditions the efficiency of hygienic practices (husbandry, milking) can be assessed by sampling of the bo vine teat canal by the wet/dry swab technique.