By using a phage vector (lambda ZAP II) and the mRNA extracted from IMR-32 cells infected with the RC.HL strain of rabies virus, we constructed a cDNA library from which four nucleoprotein (N)-specific cDNA clones were obtained by Southern blot hybridization. These clones contained a cDNA insert of about 1.4 kb, in which the longest open reading frame was the same length as that reported for the N cDNA of three fixed strains, CVS, PV, and SAD B19. When the nucleotide and deduced amino acid sequences were compared between the RC HL and the three strains, homology was within the range of 91.5-91.8% and 95.1-96.0%, respectively. Of 183 nucleotides of the RC.HL N-cDNA that were not identical to that of the corresponding site of at least one of the three strains, 41 were shared with the CVS strain, whereas only three were shared with either of the other two strains. In the amino acid sequence, we found 29 residues that were not shared in common with all of the four strains, 11 of which were the substitutions with radically different amino acids that might cause conformational changes of the protein, and, in addition, five of which were located in the region close to the C terminus. The number of such amino acid substitutions between the RC.HL and CVS strains was smaller than that of the other three strains. These results are not inconsistent with the presumption that the RC HL and CVS strains originated from the same laboratory strain of the Pasteur viruses.