Background The relationship between the presence of metalloproteinases and thyroid cancer remains unknown,and many controversies still exist in this field.The objective of this study was to investigate the correlations between papillary thyroid cancer and peripheral blood levels of matrix metalloproteinase-2,matrix metalloproteinase-9,tissue inhibitor of metalloproteinase-1,and tissue inhibitor of metalloproteinase-2.Methods The correlations were studied by detecting the levels of matrix metalloproteinase-2,matrix metalloproteinase-9,tissue inhibitor of metalloproteinase-1,and tissue inhibitor of metalloproteinase-2 by enzyme-linked immunosorbant assay and reverse-transcription polymerase chain reaction in the peripheral blood of 30 patients with papillary thyroid carcinoma,27 patients with benign thyroid disease,and 25 healthy volunteers.Results The levels of matrix metalloproteinase-2,matrix metalloproteinase-9,tissue inhibitor of metalloproteinase-1,and tissue inhibitor of metalloproteinase-2 in the peripheral blood of patients with papillary thyroid carcinoma were significantly higher than those in the peripheral blood of patients with benign thyroid disease and healthy volunteers (P ＜0.05).However,there were no significant differences between patients with benign thyroid disease and healthy volunteers (P ＞0.05).The accuracy of detection by both enzyme-linked immunosorbant assay and reverse-transcription polymerase chain reaction in the papillary thyroid cancer group was 83.33％.Conclusions The levels of matrix metalloproteinase-2,matrix metalloproteinase-9,tissue inhibitor of metalloproteinase-1,and tissue inhibitor of metalloproteinase-2 in the peripheral blood are helpful in identifying thyroid carcinoma and aid in preoperative assessment.