. The genotypes of growth hormone gene polymorphisms (GH-DdeI, GH-MspI, GH-HaeII, GH-ApaI, GH-CfoI) were determined in 78 pigs [Czech Large White sires (CLWsire line) ? Polish Large White (PLW) sows, Polish Large White sires ? Polish Large White sows], by the PCR-RFLP method. Preliminary studies found only GH DdeI polymorphism to be associated with performance traits. The associations of this polymorphism with growth and carcass traits were investigated. The linear model included the effects of candidate genes, genetic groups, sex and linear covariables of age at slaughter and body weight at weaning. The DdeI polymorphism of the GH gene showed associations with carcass length (P 0.05), average daily gain from birth to weaning (P 0.05) and average daily gain from weaning to slaughter (P 0.05). The association of GH genotypes with feed conversion was near significance. Sex influenced average daily gain from birth to weaning. The genetic groups (Czech or Polish sires) improved fat thickness at sacrum point 3, average daily gain from birth to weaning, lean meat content, weight of chop, weight of shoulder, weight of neck and average daily gain from weaning to slaughter. The regression on age at slaughter and on body weight at weaning influenced the majority of production traits.