Porcine reproductive and respiratory syndrome virus (PRRSV) ORF2 contains an internal ORF that codes for a small non-glycosylated protein known as 2b. Previous work had identified the presence of a 10kDa 2b protein in virus-infected cells and the induction of an anti-2b response in PRRSV-infected pigs, as well as a possible association of 2b with the virion (, Virology 287:183-191). In this study, we utilized two experimental approaches, including the use of a 2b peptide-specific monoclonal antibody, to demonstrate that the PRRSV 2b protein is an integral component of the PRRSV virion. This study suggests that 2b in PRRSV is similar to the E protein in EAV and forms a minor structural component of the virion.