The current study was carried out to investigate the impact of season of birth, age of the cows, time of first insemination, intervals between inseminations and diseases on fertilization, conception, pregnancy and days open in Belarusian cows. Moreover, «Hysterosan-MK» and «Fertilifil-K» were used for treatment of cows with endometritis. There was insignificant difference in our studies between the reproductive parameters and the season of the year, as well as age of cows. Only 15.7% of the cows were inseminated in the optimal period – 55-74 days, with a standard service period. In 48.3% of cows, the first insemination was carried out too late, and it was after 94.3±5.2 days. The service period of these cows exceeded the standard norm by 56 days. It was characterized by highest number of inseminations (2.7±0.05 times) accompanied with the lowest fertilization rate (7.1%). Cows inseminated for the first time in optimal terms had a fertilization rate of 65.2% and the number of artificial inseminations of 1.3±0.04 times. An extension in the period before the first insemination, followed by low fertilization rate was observed in those investigated cows. That extension may be referred to metabolic disorders and unbalanced ration. The results also declared that an improvement of the fertility of diseased cows was achieved after treatment with «HysterosanMK» and «Fertilifil-K» whereby it reached 43.1% and 95.4% respectively. In conclusion, it is economically expedient to carry out the first insemination in the period between 55-74 days. The total economic loss from barrenness for the analyzed animals amounted to 326. 743.7 US dollars or 450.6 US dollars per cow.