The aim of this study was to evaluate the prevalence and etiological agents of subclinical mastitis at the end of lactation in nine dairy herds in North-East Poland. In total, 387 Polish HF were involved in the study. The diagnosis of mastitis was performed on the basis of clinical examination of the udder, macroscopic evaluation of milk, determination of somatic cell count and bacteriological examination of milk. Subclinical mastitis was found in an average of 36.7% (range from 21.0% to 53.1%) of cows and of 15.7% (range from 9.6% to 25.2%) of quarters. Coagulase negative staphylococci (CNS; 31.6% of quarters), Streptococcus (Str.) agalactiae (15.6% of quarters), Staphylococcus (Staph.) aureus (12.1% of quarters) and fungi (12.2% of quarters) were most frequently isolated from subclinical mastitis. Etiological agents of subclinical mastitis differed strongly between herds. The results of this study showed that the incidence of subclinical mastitis at the end of lactation in dairy herds in North-East Poland is high. CNS were the most frequently isolated from subclinical mastitis cases, however mastitis caused by the contagious pathogens Str. agalactiae and Staph. aureus is still a problem. The fungal infections of the mammary gland also play an important role.