Abstract: Objective: To investigate the clinical factors related to the prognosis of papillary thyroid carcinoma. Methods: The clinical materials and follow-up data of 1574 cases with papillary thyroid carcinoma seen in Tianjin Cancer Institute & Hospital from June 1954 to December 1996 were analyzed retrospectively. The prognostic index (PI) of patients was calculated on the basis of the results of multivariate analysis. According to PI values, patients were classified into different hazard groups. Results: The 5-, 10-, 15-, and 20-year survival rates were 96%, 92%, 89%, and 86%, respectively. Univariate analysis showed that gender, age, lymph node metastases, distant metastases, tumor size, extent of tumor invasion, surgery modality, and clinical stage were associated with prognosis. Multivariate analysis showed that gender, age, tumor size, extent of tumor invasion, clinical stage, and distant metastases were prognostic factors. The patients were classified into low-risk, moderate-risk and highrisk groups according to the PI value. The 5-, 10-, 15-, and 20-year survival rate was 99.6%, 98.3%, 97.7%, and 95.1% in the low-risk group; 95.5%, 87.8%, 84.7%, and 81.1% in the moderate-risk group; and 64.0%, 49.5%, 29.4%, and 19.3% in the high-risk group. There was a significant difference among the groups (P<0.05). Conclusion: Gender, age, tumor size, extent of tumor invasion, clinical stage, and distant metastases are important prognostic factors in papillary thyroid carcinoma. Moreover, PI value can be used to develop a prognosis for patients with PTC.