We previously determined the 3' proximal 5,824 nucleotides of the Sendai virus genome RNA (Nucleic Acids Res. 11, 7317-7330, 1983; Nucleic Acids Res. 12, 7965-7973, 1984), and present here the sequence of the remaining 5' proximal 9,559 nucleotides. Thus, this is the first paramyxovirus to have its genome organization elucidated. The set of complementary DNA clones used was prepared by the method of Okayama and Berg from polyadenylylated viral genome RNA. We sequenced the region containing the 5' proximal half of the F gene, and the subsequent HN and L genes, and predicted the complete amino acid sequence of the products of these genes. Sequence analyses confirmed that all the genes are flanked by consensus sequences and suggest that the viral mRNAs are capable of forming stem-and-loop structures. Comparison of the F and HN glycoproteins of Sendai virus with those of simian virus 5 strongly suggests that the cysteine residues are highly important for maintenance of the molecular structures of these glycoproteins.