Calsarcins comprise a novel family of muscle-specific calcineurin-interacting proteins and play an important role in modulating both the function and substrate specificity of calcineurin in muscle cells. In this study, we cloned and characterized calsarcins from pig muscle. The deduced amino acid sequences of porcine calsarcin-1 (CS-1), calsarcin-2 (CS-2), and calsarcin-3 (CS-3) share the same putative calcineurin and alpha-actinin binding regions. Radiation hybrid mapping data indicate that CS-1 and CS-2 map to q2.1-2.5 of pig chromosome 8 (SSC8) and q2.4 of pig chromosome 14 (SSC14), respectively. The mRNA expressions of both CS-1 and CS-2 are regulated in skeletal muscle similarly during postnatal development but not during prenatal development, indicating differences in function, additionally demonstrated by minute differences in cellular localization within Pig Kidney Epithelial cells (PK15). We provide the first evidence that CS-1 is abundantly expressed in porcine heart and has an expression pattern similar to the human gene. This result suggests that the pig may be a suitable animal model to study the function of calsarcins in human heart disease.