Background/Purpose: As endoscopic equipment and instruments have been improved, the indication for endoscopic surgery has been extended. The authors achieved endoscopic membranectomy for congenital membranous stenosis in the upper gastrointestinal tract. Methods: Case 1 was a 3-year-old girl with membranous stenosis in the descending duodenum. Case 2 was a 1-year-old boy with esophageal membranous stenosis. In case 1, a flexible endoscope with a banding chamber, the inside of which had a tiny groove for a high-frequency-wave snare, was inserted into the duodenum. The diaphragm was drawn into the chamber by endoscopic suction and tied with the snare around its base, then dissected by electrifying the snare. In case 2, the diaphragm was resected with a high-frequency-wave cutter, assisted by a balloon catheter pulling up the diaphragm from the distal side. Results: In both cases, the stenosis was released adequately without complications, and oral feeding was restarted in a day after the procedure. Conclusions: Endoscopic membranectomy using a high-fre-quency-wave snare/cutter was achieved safely and effectively in 2 children with congenital membranous stenosis in the upper gastrointestinal tract. Background / Purpose: As endoscopic equipment and instruments have been improved, the indication for endoscopic surgery has been extended. The authors achieved endoscopic membranectomy for congenital membranous stenosis in the upper gastrointestinal tract. Methods: Case 1 was a 3-year-old girl with membranous stenosis in the descending duodenum. Case 2 was a 1-year-old boy with esophageal membranous stenosis. In case 1, a flexible endoscope with a banding chamber, the inside of which had a tiny groove for a high-frequency-wave snare , was inserted into the duodenum. The diaphragm was drawn into the chamber by endoscopic suction and tied with the snare around its base, then dissected by electrifying the snare. In case 2, the diaphragm was resected with a high-frequency-wave cutter, assisted by a balloon catheter pulling up the diaphragm from the distal side. Results: In both cases, the stenosis was released adequately without complications, and oral feeding was restarted in a day after the procedure. Conclusions: Endoscopic membranectomy using a high-fre-quency-wave snare / cutter was achieved safely and effectively in 2 children with congenital membranous stenosis in the upper gastrointestinal tract.