It is currently debated whether identification of ESR (estrogen receptor) genotypes should be introduced into breeding programs of Large White pigs. The aim of this study was to evaluate the possible relations between ESR/Ava I polymorphism and carcass performance traits in Polish Large White boars. We examined 103 boars originating from one herd in NE Poland. ESR/Ava I genotypes were determined by the PCR-RFLP method. By the use of the Duncan test, we found highly significant differences (P < 0.01) between WW and MW genotypes, as well as significant differences (P < 0.05) between WW and MM genotypes for meatiness. No significant differences were found for daily gain and selection index.