Porcine circovirus type 2 is considered as one of the most important pathogens of swine. The identification and correlation of PCV2 with PMWS, was followed by an increasing isolation of the virus from pigs suffering from various syndromes and disease problems. Infection by PCV2 has been associated with systemic disease, porcine dermatitis and nephropathy syndrome, porcine respiratory disease complex and reproductive disorders. Moreover, PCV2 has been associated with congenital muscular tremor type AII, proliferative and necrotizing pneumonia, acute pulmonary edema, granulomatous enteritis and necrotizing lymphadenitis. Despite the evidence of PCV2 association with all these syndromes and disorders, still there is a lack of knowledge concerning the relative pathogenic mechanisms.