A novel expressed sequence tag (ESThp9-1, GenBank accession number: B1596262) was isolated from pig skeletal muscular tissue by using the mRNA differential display technique. BLAST analysis revealed that the 196 bp long EST (ESThp9-1) was not homologous to any of the known porcine genes in the database but similar to rat U3A small nuclear RNA (87% identity over 93 nucleotides) and mouse U3B.4 small nuclear RNA (85% identity over 96 nucleotides). Semi-quantitative reverse transcription polymerase chain reaction indicated that EST9hp-1 was expressed in most of tissue of the pig. ESThp9-1 was physically mapped on sus scrofa chromosome 12q1.1-q1.5 and linked with microsatellite S0090 by using somatic cell hybrid panel and radiation hybrid panel analysis. According to the homologous information and result of physical mapping, ESThp9-1 was presumed to be one member of the porcine U3 gene family.