Abstract: Objective:To assess the clinical efficacy of CT-guided radioactive iodine-125 seed implantation in treating pancreatic cancer. Methods: CT-guided radioactive I-125 seed implantation was applied in21patients with end-stage unresectable pancreatic cancer. Treatment Planning System was used to reconstruct a 3-di-mensional image of the tumor and to define the quantity and distribution of I- 125 seeds. Iodine-125 seeds (0.5-0.8 mCi/seed) were introduced into pancreatic tumors under CT guidance, 1 to 1.5 cm apart, avoiding puncturing vessels, pancreatic tubes or adjacent structures. Results: Of the 21patients involved, there were 13males and 8 females. Patient age ranged from 40to 89years, with an average of 67. The median diameter of the tumors was 5.9 cm. Post-treatment follow up duration was 2 to 25months. Patients reported pain relief at2 to 5 days after implantation. Repeated computed tomography performed 2 months later revealed complete relief (CR) in2 cases, partial relief (PR) in 12cases, no changes (NC) in 2 cases and progression (PD) in5 cases. The overall effective rate (CR+PR) was 61.9%. Median survival time was8.7 months for all patients,11months for patients of stage Ⅱand Ⅲ, and 6 months for patients of stage Ⅳ. The cumulative survival rates at 3, 6 and 12months were 100 %, 71.4% and 28.6%, respectively. The 6- cumulative survival rates for stage Ⅱ+ Ⅲand stageⅣpatients were 91% and 55%, respectively; the12-month cumulative survival rates were 50% and 0%, respectively. Of the 12patients with elevated Ca-199 at baseline,8 cases had lowered Ca-199 levels after intervention, and 6 of them had levels decreased to less than50% of the original. Two seeds of I-125 migrated to the liver in 1 patient. There were no serious complications such as GI bleeding, pancreatitis, pancreatic fistula formation or radiation colitis during follow-up. Conclusion: CT-guided I-125 seed implantation is a safe, effective and less complicated treatment option for advanced pancreatic cancer, achieving pain relief and improvements in short-term quality of life.