Abstract. The aim of the study was to identify the detailed impact of the season, parity and breed on reproductive performance of sows. The experimental material consisted of 2100 sows, in 3 breed variants: 700 PL, 700 PLW, 700 crossbreeds PL × PLW. Sows were observed until parity 5. In the context of the breed, depending on the order of parity groups of 140 sows were isolated. Then, sows were divided in terms of farrowing season into subgroups numbering 35 sows. At the age of 8 months gilts were allocated for reproduction performance. The highest seasonal impact was noted for piglet birth weight (P≤0.01). Parity had less effect only on the number of piglets weaned (P≤0.05). Breed influenced to a lesser extent the number of piglets born live and weaned (P≤0.05), while birth and weaning weight had greater importance for piglets (P≤0.01). The interaction between the studied factors was also observed. The impact of season, parity and breed interdependence on the number of piglets born live were confirmed statistically (P≤0.05). The analysis of piglet birth weight allowed the stronger interaction effect of parity × breed on this parameter to be noted (P≤0.01). The analysis of variance for piglet weaning weight confirmed strong relations between all tested factors (P≤0.01). Our study has shown that reproductive parameters can be strongly affected by season and parity. In addition, it must be emphasized that the impact of these factors was different for the studied breeds of sows.