The results of analyses of the 5'-terminal sequences of Fowl Plague virus RNAs are presented. The first 13 residues of each of the eight RNA molecules which constitute the genome are in the identical sequence 5'AGUAGAAAUUAGG- and this conservation of sequence is shown to extend to other influenza viruses. The 5'-terminal sequences of virion RNA transcripts produced in vitro are also reported and again the first 12 nucleotides of these are identical for all influenza type A transcripts examined in the sequence 5'AGCAAAAGCAGG-. In addition the results of attempts to determine the sequence relationship between vRNAs and the two classes of complementary RNA synthesized in influenza infected cells are described which support the conclusion that influenza messenger RNAs are incomplete transcripts.