The nucleotide sequence of the genomic 3' terminal region (1,702 bases) of two Brazilian Bidens mosaic virus isolates (BiMV: BiMV-p and BiMV-b) was determined. BiMV-p and BiMV-b share 98% nucleotide sequence identity, and are most closely related to members of the potyvirus species: Sunflower chlorotic mottle virus (an isolate of Potato virus Y) and Potato virus Y. BiMV-p shares 88% capsid protein amino acid identity and 77% 3'UTR nucleotide sequence identity with SuCMoV an isolate of Sunflower chlorotic mottle virus. Phylogenetic analyses suggest the close evolutionary relationship of BiMV, SuCMoV and Potato virus Y (PVY), members of the PVY species. According to the analyses of capsid protein and 3'UTR sequences BiMV isolates must be regarded as a strain of Potato virus Y species, but their differences in host reactions and the phylogenetic distance suggest that they would be most likely better placed in a taxon between species and strains.