CapZ is a widely distributed and highly conserved actin-binding protein that caps the barbed end of actin filaments and nucleates actin polymerization in a Ca(2+)-independent manner. In myofibrils, it is localized in the Z-lines. In this study, we cloned and characterized Capz subunit genes from the pig muscle. The nucleotide sequences and the predicted protein sequences share high sequence identity with other mammalian orthologs. The reverse transcriptase polymerase chain reaction (RT-PCR) revealed that porcine Capzbeta, Capzalpha1, and Capzalpha2 genes are expressed in all 11 tissues studied (liver, spleen, small intestine, large intestine, lymph node, kidney, heart, skeletal muscle, brain, fat, and lung) but in variable amounts. Radiation hybrid mapping data indicated that Capzbeta, Capzalpha1, and Capzalpha2 map to q2.1-2.6 of pig chromosome 6 (SSC6), q1.6-q2.2 of pig chromosome 4 (SSC4), and q1.3-2.3 of pig chromosome 18 (SSC18), respectively. An A/C single nucleotide polymorphism in Capzbeta intron 4 was identified with a HhaI PCR restriction fragment length polymorphism, which showed great allele frequency differences between Guizhou Xiang, Guangxi Bama, Wuzhishan, Tongcheng, Landrace, and Yorkshire pigs. The association analysis suggested that the Capzbeta genotype was associated with leaf fat (P < 0.05) in our experimental population.