Carnitine acetyltransferase (CRAT) is an important enzyme for energy homeostasis and fat metabolism. We characterized the predicted full length cDNA sequence of the porcine CRAT gene. Its structure is very similar to that in humans with respect to the size and organization of the 14 exons. We demonstrated the existence of a porcine alternative transcript resulting from a partial intron-retention at the 5' end of exon 2. To perform a comparison of the 5' end variants of the mammalian CRAT gene, we analyzed the Genbank data, and here we propose a new 5' variant for dog, rat and mouse. In contrast to other mammals where this variant encodes a shorter protein (-21 aa in human, mouse and rat, and -14 aa in dog), the pig variant encodes for a longer protein (+18 aa). In all mammalian species, variant 1 has a high probability of a preferential mitochondrial sub-cellular localization. Nevertheless, it is not evident, in particular in porcine and dog species, that the second variant is associated with a different sub-cellular specificity.