The complete nucleotide sequences of beet necrotic yellow vein virus RNA-1 to RNA-4 of the Japanese isolate S (BNYVV-S) were determined and compared with those of French isolate (BNYVV-F2). The nucleotide sequences of the two isolates were very similar, differing by only 1.7% (RNA-1), 4.1% (RNA-2), 2.9% (RNA-3) and 3.6% (RNA-4), respectively. The differences of the amino acid sequences of the two isolates depended upon the open reading frames (ORF) as follows: P237, 1.4%; P22 (coat protein), 2.1%; 54k ORF, 3.4%; P42, 0.5%; P13, 1.7%; P15, 3.0%; P14, 7.0% P25, 6.4%; P31, 3.5%. Comparison of the coat protein and triple gene block (P42, P13 and P15) regions of RNA-2 with other isolates revealed that BNYVV-S was much more similar to the Yugoslavian isolate (BNYVV-Yu2) than to BNYVV-F2. The nucleotide differences between BNYVV-S and BNYVV-Yu2 were less than 1%. Based upon the grouping of BNYVV variants reported by Kruse et al. [10], BNYVV-S is thus considered to belong to the A type along with BNYVV-Yu2, whereas BNYVV-F2 is classified in the B type. Our data suggest that the Japanese isolate S may have been derived from European countries other than France or Germany.