Genome segments 2 and 3 were completely sequenced for one virulent and one avirulent bluetongue serotype 17 (BLU-17). These two segments were previously shown to exhibit virulence-associated markers. The marker on segment 2 was characterized as a change in the neutralization domain on its protein product, VP2. The nucleotide sequences for segments 2 were 94.5% identical, and their predicted proteins differed by 34 amino acids or 3.7%. Three clusters of variability were identified which may be involved with viral neutralization. These variable regions were compared to mutations for published monoclonal antibody-resistant variants of BLU. The marker on segment 3 was characterized as a mobility shift in polyacrylamide gel electrophoresis (PAGE). The nucleotide sequences were 95.0% identical, and their predicted proteins differed by four amino acids or 0.4%. These amino acid changes were relatively conserved; therefore, they are not likely responsible for virulence. The segment 3 sequences were compared to published sequences, and evidence was found to suggest that the virulent isolate had naturally reassorted between a BLU-17 and BLU-10 isolate.