Poor perfusion of the gastric substitute in esophageal replacement frequently causes anastomotic break down. In this in vivo study we assessed gastric microperfusion before, during, and after gastric tube formation by means of laser Doppler flowmetry in 11 patients undergoing esophagectomy for esophageal cancer. Baseline blood flux along the greater curvature was 323 +/- 57, 167 +/- 28, and 190 +/- 44 perfusion units (PU) and along the lesser curvature 222 +/- 44 and 227 +/- 46 PU. Blood flux was significantly higher in close proximity to tumor-infiltrated areas (819 +/- 172 and 879 +/- 119 PU, P < 0.03 and P < 0.008 compared to normal stomach). Dissection of the gastrocolic ligament and the left gastric artery reduced gastric blood flux along the greater curvature to 69 +/- 21, 79 +/- 19, and 155 +/- 61 PU. Elongation and transformation of the stomach to a gastric tube further reduced blood flux in the stomach especially at the fundus. In this study laser Doppler flowmetry was a valuable tool to assess microcirculatory changes during gastric tube formation as well as pathological blood flow in tumor bearing areas of the stomach in vivo. Quantification of the perfusion of gastric tubes in esophageal replacement might help prevent ischemia-induced anastomotic breakdown.