The prevalence of anastomotic strictures in esophageal anastomoses provides us with limited information about the anastomotic healing process. This prospective study evaluates the exact esophageal anastomotic diameters in 256 patients who underwent esophagectomy and esophagogastrostomy without pyloroplasty (n = 107) or total gastrectomy and Roux reconstruction (n = 149). No perioperative chemoradiotherapy was given. Anastomotic strictures and diameters were assessed during endoscopy by a separately inserted (inflated to the anastomotic width) balloon catheter. The anastomotic diameters increased significantly during the first postoperative year in the esophagectomy (p = 0.001) and gastrectomy (p < 0.001) groups. The anastomoses in the gastrectomy group were significantly wider than those in the esophagectomy group 3 (25.7 versus 19.9 mm), 6 (28.5 versus 22.0 mm), and 12 (30.5 versus 23.3 mm) months after surgery (p < 0.001). Neither the anastomotic site (neck or chest) in the esophagectomy group (p = 0.176) nor that in the gastrectomy group (abdomen or chest) (p = 0.577) influenced the anastomotic diameter. Benign anastomotic strictures were most frequently found after 3 months and after esophagectomy. Esophagojejunostomies performed with 2 linear stapling devices or cartridge size 28 mm showed the widest anastomoses with only 1 stricture. Esophagogastric anastomoses following esophagectomy are narrower and develop more strictures than esophagojejunal anastomoses after total gastrectomy, but both dilate during the first year.