Objectives: Hereditary hemorrhagic telangiectasia is an autosomal dominant di sease in which 25% to 30% of patients will develop gastrointestinal bleeding from telangiectases. The extent of telangiectases has not been previously evalu ated. This cross- sectional study compared the presence, number, and size of te langiectases in the stomach and duodenum to those in the jejunum using enterosco py. Methods: At the Yale University Vascular Malformation Center, 30 consecutive , symptomatic adult patients with hereditary hemorrhagic telangiectasia were eva luated using a 220- cm- length enteroscope. The number and size of the telangi ectases were documented in the esophagus, proximal and distal stomach, four part s of the duodenum, and every 20 cm in the jejunum. The indication for the proced ure was recorded as anemia, gastrointestinal bleeding, or anemia out of proporti on to epistaxis. Results: The results of 27 patients were analyzed. A total of 8 9% of patients had telangiectases in the first 60 cm of the jejunum. In indivi dual patients, there was a strong correlation between the number of telangiectas es in the stomach/duodenum when compared with the jejunum. In group analysis, th e median number of telangiectases in the stomach and duodenum was significantly higher than in the jejunum (13 vs. 3; Wilcoxon signed rank test, P = 0.001). The presence of large (≥ 5 mm) telangiectases in the stomach/duodenum did not nece ssarily indicate that there would be large telangiectases in the jejunum. Conclu sions: The presence and number of stomach and duodenal telangiectases correlated with the presence and number of jejunal ones. However, the occurrence of large proximal telangiectases was not associated with large distal ones. Objectives: Hereditary hemorrhagic telangiectasia is an autosomal dominant diase in which 25% to 30% of patients will develop gastrointestinal bleeding from telangiectases. The extent of telangiectases has not been previously evaluated ated. This cross- sectional study compares the presence, number, and size of te langiectases in the stomach and duodenum to those in the jejunum using enterosco py. 30: At the Yale University Vascular Malformation Center, 30 consecutive, symptomatic adult patients with hereditary hemorrhagic telangiectasia were eva luated using a 220- cm- length enteroscope. The number and size of the telangi ectases were documented in the esophagus, proximal and distal stomach, four part s of the duodenum, and every 20 cm in the jejunum. The indication for the proced ure was recorded as anemia, gastrointestinal bleeding, or anemia Out of proportions on epistaxis. A total of 8 9% of patients had telangiectases in th e first 60 cm of the jejunum. In indivi dual patients, there was a strong correlation between the number of telangiectas es in the stomach / duodenum when compared with the jejunum. In group analysis, th e median number of telangiectases in the stomach and duodenum was significantly higher than in the jejunum (13 vs. 3; Wilcoxon signed rank test, P = 0.001). The presence of large (≥ 5 mm) telangiectases in the stomach / duodenum did not nece ssarily indicate that there would be large telangiectases in the jejunum. Conclu sions: The presence and number of stomach and duodenal telangiectases correlated with the presence and number of jejunal ones. However, the occurrence of large proximal telangiectases was not associated with large distal ones.