The fatty acid composition, the amount of free fatty acids and primary and secondary products of oxidation were investigated in relation to quality of raw cows milk produced and stored at a farm with a central milk duct. Raw milk samples were collected from the evening milking, from bulk milk (evening and morning milkings) and from animals with signs of subclinical mastitis. It was established that bulk milk and the milk from cows with subclinical mastitis contained more short- and medium-chain saturated fatty acids (С4:0 to С16:0) and less long-chain unsaturated fatty acids (С18:1 and С18:2), mainly because of the altered amount of oleic and linoleic acids. In mastitic milk, apart the increased somatic cell counts, increased values of free fatty acids (FFA), peroxide value and malondialdehyde (MDA) concentrations were found out, while total phospholipids were decreased. Similar tendencies in FFA, peroxide value and MDA were established in bulk milk samples. The main reason for these changes were oxidative changes in bulk milk in the milk collection tank