The mRNA differential display technique was performed to investigate differences in the gene expression in the musculus longissimus from Wujin and Large White pigs. A fragment of one differentially expressed gene was isolated and sequenced. A complete cDNA sequence was obtained using the rapid amplification of cDNA ends (RACE) method. The sequence prediction analysis revealed that the open reading frame of this gene encodes a protein of 1 103 amino acids, which is homologous with the ubiquitin specific peptidase 7 (USP7) of four species, rat (identity 98%), human (98%), mouse (98%) and chicken (95%), so it can be defined as the porcine USP7 gene. The differences in the USP7 gene expression in muscles from Wujin and Large White pigs were confirmed using semi-quantitative RT-PCR. The gene expression analysis in eight tissues of a Wujin × Large White cross showed that USP7 was expressed in all the tissues, except for fat.