The aim of this work was to determine the dependency between polymorphism in the PIT-1and fertility rates, body weight of cows and calves, the course of parturition and viability of calves in Polish Black-and-White Holstein-Friesian cattle. The analysis included 1024 cows and 3663 calves of the Polish Black-and-White Holstein-Friesian breed (phf). The study included an analysis of one polymorphic place PIT-1 (c.1178G>A). The source data used to calculate the indicators of reproduction were collected from cows inseminated by semen of Black-and-White Holstein-Friesian bulls and giving birth to single calf. The following information was taken from each animal: age at first insemination, age at first calving, number of semen portions attributable to successful insemination, length of pregnancy and periods of: insemination service, postpartum resting period, interpregnancy period and intercalving period. The study also determined weight of the cow and weight of the calf at calving (including gender). Statistical calculations were performed using the statistical package SAS v.9.3. The following procedures were used: MEANS and GLM. In black and white Holstein-Fresian cattle there is genetic variety in analysed locus c.1178G>A gene PIT-1. Frequency of genotypes and alleles was respectively: AA=0.0469, AG=0.3154, GG=0.6377, A = 0.2046 and G = 0.7954. AA homozygotes had the highest age at first insemination and the lowest insemination index. Cows with this genotype after calving and calves (both gender) from AA homozygotes had the biggest weight after calving. In contrast GG homozygotes had the longest intercalving period. The results prove the existence of dependencies between genu PIT-1 gene polymorphism in locus c.1178G>A, reproductive potential and body weight of cows and calves. More favorable results were observed in AA homozygotes. It is possible to use these dependencies in genetic selection of farm animals. In order to confirm the obtained results it would be advisable to conduct studies in a larger population of cows with consideration of other breeds.