Local blood flow changes in association with proximal gastric vagotomy were studied with laser Doppler flowmetry in 10 patients. After the vagotomy a significant decrease in blood flow amounting to 57 +/- 21% (range, 18-87%; p less than 0.001) was observed within the dissected area along the lesser curvature. In three patients, the flowmeter recordings suggested localized areas with very poor perfusion. The blood flow was restored to preoperative control values within 3-4 weeks after the operation. It is suggested that the temporary poor blood perfusion along the lesser curvature may be an important factor in the genesis of postoperative ulcerations in the dissected area. We conclude that laser Doppler flowmetry seems to have great potential as a method to study localized blood flow changes in the stomach. Flowmeter recordings can be made both during operation and endoscopy.