The cDNA sequence of the Mcl-1 protein was determined from a porcine model (Sus scrofa) and is compared to the corresponding genes of rat, human, and zebrafish. Multispecies comparison of the diversity of the Bcl-2 superfamily demonstrates Mcl-1 homology between the rat, human, and zebrafish. Porcine Mcl-1 cDNA has a size of 2487 nucleotides and encodes a polypeptide of 152 amino acids. Porcine Mcl-1 shares 83.9%, 85.3%, and 50.0% similarity to rat, human, and zebrafish Mcl-1, respectively. Real-time quantitative PCR analysis revealed that Mcl-1 transcripts are highly expressed in the uterus, lung, and liver. Despite these small molecular differences in expression, our results indicate that the structure of porcine Mcl-1 protein appears to have been remarkably conserved, and it may be involved in regulation of apoptosis.