Selection and genetic parameters allow defining optimum directions in the organization of selection and breeding work. The research objective was the determination of selection and genetic parameters of cows’ milk efficiency. The object of the research- es was the livestock of cows of black and motley breed numbering 255 heads bred in breeding plant of Federal State Unitary Enterprise ‘Omskoye’. Se- lection and genetic parameters of cows of various production groups bred on the farm were studied. The coefficient of inheritance of milk yield on herd averaged 0.237, with extreme deviations from0.119 to 0.341. The inheritance of milk fat content was in the limits 0.380-0.482. The accounting of interrelation between economic and useful signs was of great importance at selection of animals. In young cows the interrelation between milk yield for lactation and milk content of fat was practically missing, the coefficient of correlation made 0.012-0.015. In full-age cows weak negative interrelation between the yield of milk and the content of milk fat was observed, the coefficient of correlation varied from -0.13 to -0.11. The cows of the fifth lactation between the yield of milk and fat had positive highly reliable correlation interrelation (r = 0.53). The re- peatability of milk yield for the first lactation with subsequent ones had curvilinear character: the co- efficients of repeatability increased to the 3rd lacta- tion, then gradually decreased. At selection of cows in a breeding core great demands were made to productive qualities of animals therefore the selec- tion differential made on milk yield was +1548 kg, and on mass fraction of milk fat of +0.1 % concern- ing the efficiency of firstcalf heifers. Receiving re- pair heifers from cows of a breeding core, it is pos- sible to expect an increase in abundant milk yield in the next generation on 352.9 kg of milk and for 0.05% according to the content of milk fat. At the organization of selection and breeding work in dairy cattle breeding it is necessary to take into account selection and genetic parameters concerning theinheritance of signs, existence between them of interrelations and repeatability of estimates.