Abstract: To explore the association between parvovirus B19 infection and the pathogenesis of papillary thyroid carcinoma (PTC). Methods: The levels of B19 DNA and virus protein were determined in tissue blocks of dissected thyroid from 38 PTC patients (30/38 cases also have normal paraneoplastic tissues) and normal paraneoplastic thyroid tissues from 16 patients with adenoma, using nested polymerase chain reaction (nPCR), in situ hybridization (ISH) and immunohistochemistry (IHC) techniques simultaneously, in a double blind manner. Results: A B19- specific DNA fragment of 173 bp was amplified using nPCR. The ISH and IHC detection showed that the B19 DNA and virus protein mainly localized to the cell nucleus and cytoplasm . In the PTC cases, the positive rate of the nPCR,ISH and IHC was 97.4% (37/38), 78.9% (30/38) and 63.2% (24/38), respectively, whereas the positive rate was only 43.8% (7/16), 12.5% (2/16) and 6.25 % (1/16) in normal paraneoplastic thyroid tissues.There was a significant difference between the two groups (for the mean of the 3 parameters, P<0.001). The positive rate of ISH and IHC in the normal paraneoplastic thyroid tissues from PTC patients was 23.3% (7/30) and 10% (3/30), respectively. There was a significant difference between the two parameters when compared to the 30 cases with PTC (ISH: 80.0% (24/30); IHC: 60.0% (18/30); both, P<0.001). Conclusion: Papillary thyroid carcinoma has a higher B19 infection rate compared to the controls, suggesting that B19 infection may play an important role in the pathogenesis of PTC.