To evaluate the effect of the PvuII polymorphism of the ESR gene on litter size and production traits in Czech Large White swine, data from 1250 sows and 3600 litters were analysed with two four-trait animal models. The traits in the first model were number of piglets born alive in 1st litter, number of piglets born alive in 2nd and subsequent litters, lifetime daily gain and lean meat percentage. The second model included number of piglets born, piglets born alive, piglets weaned and litter weight at weaning from all litters. The ESR locus significantly affected prolicacy in the first parity and averaged over all parities (P < 0.05), with allele A superior to allele B. In the first parity, AA sows produced approximately 0.5 more live piglets per litter than BB sows. Averaged over all parities, this difference was circa 0.25 piglets. Results for total number of piglets born and number of piglets weaned were similar to results for numbers born alive.