The objective of this work was to evaluate the association of bimodality of milk flow curves with microbiological status of mammary glands and parity of cows. We selected 167 primiparous and 148 multiparous Lithuanian Black and White dairy cows in 2nd to 4th month of lactation. The bimodality of milk flow was determined in 22.2% primiparous and in 38.6% multiparous cows (P less than 0.001). The most prevalent pathogens of mastitis were Staphylococcus aureus (15.3%), other staphylococci (22.2%) and streptococci (5.8%). Prevalence of mastitis pathogens in multiparous cows was 1.4 times and the bimodality of milk flow curves –1.7 times higher in comparison with primiparous cows (P less than 0.001). The bimodality of milk flow curve was mostly associated with the prevalence of Streptococcus agalactiae and Staphylococcus aureus (P less than 0.001). The increased frequency of mastitis pathogens (21.5%) in cows with the bimodal milk flow curves supports the negative effect of bimodality on udder health of cows (P less than 0.001).