A mouse DNA polymerase delta (Pol delta)-encoding cDNA (pol delta) was isolated by PCR amplification and cDNA library screening. The sequenced cDNA has a length of 3386 bp and the open reading frame (ORF) encodes a protein of 1105 amino acids (aa) with an M(r) of 123,743. The aa identity to the proteins encoded by the corresponding cDNA from Bos taurus (93%) and Homo sapiens (92%) is very high. The identity to the Pol delta from Schizosaccharomyces pombe, Saccharomyces cerevisiae and Plasmodium falciparum is around 50%. An aa comparison between all available Pol delta sequences reveals several common structural motifs. Polyclonal antibodies raised against a 31-aa synthetic peptide deduced from the ORF specifically recognize Pol delta polymerases from human cells and calf thymus in an immunoblot.