Piétrain boars of different ryanodine receptor (RYR1) genotypes (NN, Nn and nn, three boars each) were mated with approximately ten Czech Large White x Czech Landrace sows (genotype NN) each to produce one litter per sow. The progeny of nn boars had a significantly higher individual weaning weight (7.31 kg vs. 6.86 kg) and average daily gain from birth to weaning (252 g/day vs. 240 g/day) than the progeny of NN boars. Furthermore, piglets from nn boars differed statistically significantly also from piglets of boars with the Nn genotype for these two traits. The litters of the NN boars were greater by 0.5 piglets than the litters of the nn boars for litter size traits, but the differences were not significant. The Nn genotype showed for all litter sizetraits and the number of stillborn piglets the best values. The difference between the genotypes Nn and nn was statistically significant at the 0.05 level for the number of piglets born alive and the number of piglets weaned.