With 268 heifers in farm breeding, udder examination has been performed for clinical mastitis during 14 days after calving. From each quarter we took secretion samples and performed bacteriological analysis. From total number of heifers, 56 of them had shown clinical signs of inflammation, and 12 were bacteriologicaly positive. By bacteriological analysis mastitis pathogens had been found, even in 14 heifers without inflammation signs, at least until the end of test period. From the total number of tested heifers in 3,35% of cases Streptococcus agalactiae have been found, 4,85% coagulase positive staphilococcae (CPS) and 1,49% Corynebacterium pyogenes. Because coagulasa positive staphilococci were the most present bacteries in the period of 14 days, we made opinion that the same are the most often mastitis pathogen. Heifers with intramammarian infections like these, represent source of infection fot other non-infected animals in herd. .