In this work we analyze a polymorphism in the porcine growth hormone gene (GH) in different populations of Iberian and Duroc pigs, and we study the association of the different alleles with growth and carcass traits in a sample of 199 Iberian pigs from the Torbiscal strain. This population includes two lines, the conservation line and a selected one, which present significant differences in some of the productive traits. The polymorphism used is a PCR‑RFLP (HhaI) localized in the gene's second exon. The association study was performed using an animal model in which the genotype was included as a fixed effect. Instead of the previous association evidences of this polymorphism with several economic traits and the difference in the allelic frequencies between the studied lines, we could not detect any association of this marker with the traits analyzed.