The connection of live weight of cows of Ukrainian black-and-white milk breed in the conditions of the Carpathian region of Lviv region in different ages with their subsequent milk productivity is established. It was investigated that live weight during the period of individual growth and development of animals has a significant impact on hopes, the content of fat in milk and the amount of milk fat. The difference in liveliness between cows with live weight at the first insemination to 300 and 361–380 kg for the first lactation was 249.3, for the second – 500.7 (P < 0.002), for the third – 97.0 kg, and for the highest – 405.5 kg (P < 0.01). Between cows with live weight at the first insemination of 361–380 and 401–420 kg, this difference was 185.1, 319.9 (P < 0.05), 38.7 and 265.3 kg respectively (P < 0.05). According to the results of the research, it can be stated that the optimum live weight during the period of raising cows at 6 months of age is a live weight of 160–180 kg, at 12 months of age it is 260–280 kg and the highest rates are obtained from cows that were growing at 18-months of age had a live weight of 360–380 kg. From the results of our research, it follows that for the Ukrainian black-and-white milk breed in the conditions of the Carpathian region of Lviv, the optimum live weight at the first insemination is 361–380 kg. The share of influence on milk production of live weight of cows during their growing period: at 6 months of age on hopes – 13.53–27.56%, on the fat content in milk – 15.18–39.70 and on the amount of milk fat 11.89–39.41%; at 12 months of age – respectively 24.65–37.84, 23.45–33.0 and 23.37–35.17%; in the 18-month – 27.38–40.93, 29.12–33.23 and 25.81–39.10%, and at the first insemination – 21.59–40.08, 31.32–39.99 and 21.52–39.88% at P < 0.05–0.001. The probable correlation coefficients between the live weight of cows at 6 months of age and the reliance on second, third and highest lactation were 0.163–0.2253 and between live weight and fat content in milk – 0.110–0.233, between live weight at 12 months of age and the expectation for the second, the third and highest lactation – 0.233–0.240 and between the live weight and the amount of milk fat – 0.127–0.202, at the age of 18 months and for the second, third and highest lactation – 0.246–0.337 and between the live weight and the amount of milk fat – 0.116–0.308, and at the first insemination – 0.135–0.195 and 0.118–0.188 respectively at P < 0.005 – P < 0.001.