Porcine reproductive and respiratory syndrome virus (PRRSV) has become one of the most common and economically significant infectious agents in the swine industry worldwide. The virus causes mild to severe reproductive failure in sows and gilts and respiratory problems in piglets. In this study, the author expressed the full-length PRRSV Nsp1a protein as a Glutathion-S-Transferase (GST)-Nsp1a fusion protein in E. coli BL-21. The full-length Nsp1a coding region of the Korean PRRSV isolate PL97-1 was amplified by RT-PCR from the genomic RNA and the cDNA amplicons were cloned into the pGEX4T-1 E, coli expression vector. The recombinant GST-Nsp1a fusion protein was used for immunization in rabbits. After a 5-shot immunization schedule, the PRRSV Nsp1a-specific antiserum was obtained. Using the PRRSV-infected MARC-145 cell lysates, immunoblotting analyses showed that these antisera specifically reacted with ${approx}18kDa$ of the PRRSV Nsp1a protein. The rabbit antisera raised against the PRRSV Nsp1a recombinant protein will provide a useful reagent to investigate the role of this protein in PRRSV replication and to diagnose infection.