The purpose of the work is to study the influence of the duration of the service and dry periods on the formation of milk productivity of cows of the Ukrainian Black-and-White dairy breed in the conditions of the western region of Ukraine. It was found that the highest milk yield and milk fat yield in the first, second and best lactations were characteristic of cows with a service period of 150 days or more. For the third lactation, these indicators were the highest in cows with the duration of the specified period 120-149 days. There was regularity found for the fat content in milk between animals with different duration of the service period. The highest milk yield and the amount of milk fat in the second, third and best lactations were observed in animals with a dry period of 45-54 days. The fat content in milk for the second and best lactations was highest in animals with a dry period of up to 45 days. There was no significant difference in the fat content in milk for the third lactation between animals with different duration of the dry period. The correlation coefficients between the duration of the service period and the milk yield, as well as the fat content in milk, depending on the farm and lactation, were in the range of -0,063 – 0,338 and -0,139 – 0,151, between the duration and the above-mentioned signs of milk productivity - within -0,155 – 0,048 and -0,136 – 0,052. The strength of the influence of the duration of the service period on milk yield and fat content in milk, depending on the farm and lactation, was 9,1-29,5 and 7,0-28,2%, and the strength of the influence of the duration of the dry period on the same indicators was within the range of 9,3-23,4 and 9,3-23,2%, respectively.