Endoscopical measurement of gastric mucosal blood flow seems to provide substantial advantages for noninvasive and repetitive scrutiny, especially in small animals. We employed a quartz probe 0.5 mm in diameter which was inserted into the gastric lumen through the forceps channel (0.8 mm in diameter) of the endoscope. Gastric mucosal blood flow determined with this probe in combination with laser Doppler velocimetry were sufficiently consistent and reproducible in the corpus as long as the tissue-to-probe distance was positioned in gentle contact with the gastric mucosa perpendicularly. Topical application of endothelin-1 produced a significant long-lasting decline in gastric mucosal blood flow, although laparotomy per se resulted in a slight decrease of the blood flow. Endoscopic measurement of gastric mucosal blood flow seems simple and reproducible with high potential for chronic studies.