Postweaning Multisystemic Wasting Syndrome (PMWS) is a recently described disease of growing pigs characterized by progressive weight loss and chronic pneumonia. PMWS was first identified in western Canada in 1995, and has now been diagnosed in the US, Europe and Asia. Since 1999, 57 pigs from 23 farms of PMWS have been diagnosed in the National Veterinary Research and Quarantine Service (NVRQS). The most common age of onset was clustered around 6-week age. The most common reported morbidity was 1-5 %, with 80% of the cases reporting 10% or less morbidity. The clinical signs were wasting, clyspnea, cough, diarrhea, pneumonia and sudden death. The characteristic histopatl~ologic lesions were depletion of lyn~phoid organs and lymphohistiocytic to gran~llornatous inflammation in nl~lltiple organs, predominantly lungs and lymphoid tissues. Type 2 porcine circovinls (PCV-2) antigen were denlonstrated in the lungs and lymphoid tissues by PCR and imm~inohistochen~istry. Coinfection were con~monly identified in the PMWS cases. 88% of the PMWS cases were infected with other agents such as PRRS, salmonella, pasteurelia spp. and others. The most conlnlon agent of coinfection in PMWS was PRRS.