Abstract. The studies concerned the reproduetive perfonnance of four generations of sows originating from families where the average number of piglets in the first three litters amounted to: 8.1–9.0 (group A), 9.1–10.0 (group B), 10. 1–11.0 (group C) and more than 11.0 (group D). 988 sows and 2964 litters were examined altogether. The average number of piglets reared up to the age of 21 days in the first three litters of sows-family founders has a significant effect on the fertility and feeundity levels of sows in the next generations. The best results are to be expected in the case of sows originating from families where the average number of piglets in three successive litters was higher than 10. Sows coming from families in which the average number of piglets on 21st day was lower do not show promise of equally good reproductive performance, in spite of higher weight gains and better appearance (resulting from better conditions in the periods of pre- and postnatal development). In the private sector there were no sows originating from family founders in the group < 9,0 while 95% of them belonged to groups with average piglet number >10,0.