Double-stranded cDNA synthesized from total polyadenylate-containing mRNA, extracted from monkey kidney cells infected with canine distemper virus (CDV), has been cloned into the PstI site of Escherichia coli plasmid pBR322. Clones containing canine distemper virus DNA were identified by hybridization to a canine distemper virus-specific, 32P-labeled cDNA. Four specific clones containing different classes of sequences have been identified. The cloned plasmids contain inserts of 800 (clone 74-80), 960 (clone 74-16), 1,700 (clone 364), and 950 (clone 40-9) base pairs. The sizes of the mRNA species complementary to these inserts are 1,500, 1,850, 1,850 and 2,500 nucleotides, respectively, as determined by the Northern technique. Three of the cloned DNA fragments were further identified as the reverse transcripts of the mRNA coding for the matrix, phosphoprotein, and nucleocapsid protein of CDV.