OBJECTIVE The purpose of the study was to examine the efficacy of treating patients with advanced gastric cancer using iodine -125 (125I) brachytherapy. METHODS Ten patients with unresectable advanced gastric cancer were selected based on their pattern of CT scans. We utilized a brachytherapy planning system to determine the distribution of the 125I seeds, their activity and quantity. The matched peripheral dose (MPD) was 110-135 Gy. 125I seeds were implanted in a single plane or biplane by an intraoperative small incision or percutaneous puncture. The post- operative hemogram, CT, KPS, pain-relieving period and survival period were recorded. RESULTS One patient developed a complete response (CR), 4 patients a partial response (PR), 3 patients showed no change (NC) and 2 pa- tients developed progressive disease (PD). The overall response rate (CR+PR) was 50% (5/10). The pain-relieving rate was 89% (8/9). The pa- tients’ appetite and KPS were improved. The longest survival period was 10 months and median life span was 4 months. There were 8 patients whose seeds fell off resulting in an expulsion rate of 3.8% (26/692). The patients showed 0-1 degree acute radio-therapeutic side-effects without other symptoms such as abdominal pain, vomitus cruentes or intestinal obstruction etc. CONCLUSION Applying 125I implantation to treat advanced gastric can- cer with a reasonable seed distribution can significantly improve clinical symptoms and their quality of life. The radioactive damage is mild. This method can be used as an important supplementary treatment for unre- sectable advanced gastric cancer. OBJECTIVE The purpose of the study was to examine the efficacy of treating patients with advanced gastric cancer using iodine-125 (125I) brachytherapy. METHODS Ten patients with unresectable advanced gastric cancer were selected based on their pattern of CT scans. We utilized a brachytherapy planning The matched peripheral dose (MPD) was 110-135 Gy. 125I seeds were implanted in a single plane or biplane by an intraoperative small incision or percutaneous puncture. The post- RESULTS One patient developed a complete response (CR), 4 patients a partial response (PR), 3 patients showed no change (NC) and 2 pa- tients The progressive response rate (CR + PR) was 50% (5/10). The pain-relieving rate was 89% (8/9). The pa tients’ appetite and KPS were improved. The longest survival period was 10 months and median life span was 4 months. There were 8 patients whose seeds fell off resulting in an expulsion rate of 3.8% (26/692). The patients showed 0-1 degree acute radio-therapeutic side-effects without other symptoms such as abdominal pain, vomitus cruentes or intestinal obstruction etc. CONCLUSION Applying 125I implantation to treat advanced gastric can-cer with a reasonable seed distribution can significantly improve clinical symptoms and their quality of life. The radioactive damage is mild. This method can be used as an important supplementary treatment for unre- sectable advanced gastric cancer.