The NH2-terminal amino acid sequence of Moloney murine leukemia virus reverse transcriptase was determined to be Thr-Leu-Asn-Ile-Glu-Asp-Glu-Tyr-Arg-Leu-His-Glu-. The comparison of the amino acid analysis data obtained after carboxypeptidase Y digestion with the published nucleotide sequence (T. M. Shinnick, R. A. Lerner, and J. G. Sutcliffe, Nature (London) 293, 543-548, 1981) led to the conclusion that the COOH-terminus is Leu coded by CTC in nucleotide positions 4608-4610, and the tentative COOH-terminal sequence is Pro-Asp-Thr-Ser-Thr-Leu-Leu-OH. In light of these and previously reported results the complexity and map order of the pol gene are discussed.