Three 7-9 week-old pigs from a farm in Nakorn Patom province having clinical signs such as dyspnea, diarrhoea, cachexia were sent to The Large Animal Hospital, Faculty of Veterinary Science, Chulalongkorn University for diagnosis. A complete necropsy demonstrated generalized lymphnode enlargement (3-4 times), enterocolitis, cranioventral pneumonia and multifocal to diffuse pneumonia. Microscopically, a depletion of lymphoid tissue and a lot of basophilic intracytoplasmic inclusion bodies were found in macrophages in tonsil, lymphnodes and Peyer patch. By electron microscopy, the inclusion bodies were inferred to be virus-like particles with 14-18 nm in diameter. The inclusion bodies were further proven by immunohistochemistry to be a porcine Circovirus (PCV). This is the first evidence of PCV infection in pigs in Thailand.