AIM:To evaluate the natural history of subepithelial lesions.METHODS:We reviewed the medical records of 104 159 patients who underwent upper gastrointestinal endoscopy at the Center for Health Promotion of Samsung Medical Center between 1996 and 2003.Subepithelial lesions were detected in 795 patients(0.76%);252 patients were followed using upper gastrointestinal endoscopy for 82.5 ± 29.2 mo(range,12-160 mo;median,84 mo;1st quartile,60 mo;3rd quartile,105 mo).The median interval of follow-up endoscopy was 12 mo(range,6-105 mo;1st quartile,12 mo;3rd quartile,24 mo).RESULTS:The mean patient age was 53 years(range,22-80 years),and the male-to-female ratio was 2.36:1(177/75).The lesion size at initial measurement averaged 8.9 mm(range,2-25 mm;median,8 mm;1st quartile,5 mm;3rd quartile,10 mm).Of the 252 lesions,244(96.8%) were unchanged and 8(3.2%) were significantly increased in size(from 12.9 ± 6.0 to 21.2 ± 12.2 mm) after a mean interval of 59.1 ± 27.5 mo(range,12-86 mo).Surgical resection of lesions was performed when the lesions were ≥ 3 cm in diameter.Two lesions were diagnosed as gastrointestinal stromal tumors with an intermediate or high risk of malignancy and one lesion was classified as a schwannoma.CONCLUSION:Most small subepithelial lesions do not change as shown by endoscopic examination,and regular follow-up with endoscopy may be considered in small,subepithelial lesions,especially lesions < 1 cm in size. AIM: To evaluate the natural history of subepithelial lesions. METHODS: We reviewed the medical records of 104 of 159 patients who underwent upper gastrointestinal endoscopy at the Center for Health Promotion of Samsung Medical Center between 1996 and 2003. Subepithelial lesions were detected in 795 patients ( 0.76%); 252 patients were followed using upper gastrointestinal endoscopy for 82.5 ± 29.2 mo (range, 12-160 mo; median, 84 mo; 1st quartile, 60 mo; 3rd quartile, 105 mo). The median interval of follow-up Results: 12 years (range, 6-105 mo; 1st quartile, 12 mo; 3rd quartile, 24 mo) .RESULTS: The mean patient age was 53 years (range, 22-80 years), and the male-to-female The lesion size at initial measurement averaged 8.9 mm (range, 2-25 mm; median, 8 mm; 1st quartile, 5 mm; 3rd quartile, 10 mm). Of the 252 lesions , 244 (96.8%) were unchanged and 8 (3.2%) were significantly increased in size (from 12.9 ± 6.0 to 21.2 ± 12.2 mm) after a mean interval of 59.1 ± 27.5 months (range, 12-86 months) ection of lesions was performed when the lesions were ≥ 3 cm in diameter. Two lesions were diagnosed as gastrointestinal stromal tumors with an intermediate or high risk of malignancy and one lesion was classified as a schwannoma. CONCLUSION: Most small subepithelial lesions do not change as shown by endoscopic examination, and regular follow-up with endoscopy may be considered in small, subepithelial lesions, especially lesions <1 cm in size.