Myogenic factor 3 (myf - 3) and myogenic factor 5 (myf - 5) are the products of genes: MYOD1 (MYF3) and MYF5, respectively, which belong to the MyoD family. These transcription factors control the processes of myogenesis. The fragments of both the genes comprising exons and promoters were amplified and sequenced. In the 5'UTR region of gene MYOD1, the G302A transition was identified and it is not recognized by any restriction endonuclease. In the promoter region of gene MYF5 we identified three mutations at positions: A65C (PCR-RFLP/AciI); C580T (PCR-RFLP/FokI) and C613T (PCR-RFLP/HinPI). Mutations C580T and C613T were characteristic for Pietrain ? (Polish Large White ? Polish Landrace) crossbred pigs named Torhyb. The C2931T transition, which is not recognized by any restriction enzyme, was identified in exon 3 of gene MYF5. This mutation results in a change of the amino acid sequence (Leu?Pro). The frequency of particular genotypes at the MYOD1 and MYF5 loci proved to be dependent on pig breed. However, Duroc pigs were monomorphic at all the SNPs presented in this study. These SNPs might be analyzed in a further study as probably influencing carcass meatiness.