A missense mutation (Asp298Asn) located in a highly conserved region of the melanocortin-4 receptor gene (MC4R) has been associated in different pig lines with backfat thickness, feed intake, growth rate and carcass composition although the results are inconsistent. In this study, 913 Iberian pigs and 28 wild boars of diverse origins were genotyped for this MC4R polymorphism, and its association with performance and quality traits was analyzed in 701 Iberian pigs with phenotypic records. The observed genotypes showed a high frequency (0,92) in the Iberian breed of the G allele (Asp298), that was monomorphic in the wild boars. The A allele (Asn298) was significantly associated with increased daily growth gain in the fattening period and lower percentage of premium cuts. A suggestive association (P <0,10) of this allele with increased intramuscular fat was also detected. The usefulness of this MC4R polymorphism for selection of Iberian pigs is discussed.