We genetically analyzed field isolates of the Newcastle disease (ND) virus isolated in Japan from 1930 to 2001. The coding region of the fusion protein was amplified by reverse transcriptase PCR and directly sequenced. Phylogenetic analysis revealed the presence of viruses belonging to six of the eight known genotypes. It can be concluded from this study that ND outbreaks in Japan have been of multiple etiologies. [All sequences used in this study were sent to DDBJ and assigned accession numbers AB 070382 to AB 074042.]