A composite 3945-bp cDNA that encodes rat pyruvate carboxylase (PC) has been constructed from clones isolated from a rat liver cell cDNA library and the nucleotide sequence has been determined. The rat cDNAs open reading frame encodes a protein of 1178 amino acids that is 98.6% identical (99.0% similar) to that of mouse PC and 96.0% identical (97.8% similar) to that of human PC.