During the last two years, the availability of effective vaccines against PCV2 and their extensive successful use under field conditions to control PMWS have allowed to convincingly demonstrate that porcine Circovirus fulfills an important etiological role in this multi-factorial syndrome. In spite of this established importance of PVC2 for PMWS, the disease continues to be considered multi-factorial and the possibility of other infectious co-factors being involved in PMWS remains a lively possibility. In this research we took advantage of a very well characterized set of samples from a PMWS-affected herd. Using highly sophisticated molecular biology techniques we attempted to ascertain if an unknown new viral agent would be involved in these well recognized cases of PCV2-associated PMWS. Our results provide evidence that important molecular disorders typical of chronic inflammations and other pathologic (not necessarily infectious) processes may also be involved in PMWS. However, we have been unable to demonstrate the presence of any other novel, yet unknown infectious agent involved din the etiology of PMWS.