Electrochemically generated hydrogen gas was used to measure pancreatic regional blood flow in dogs by Koshu's method. This method is not necessary to inhale H2 gas and it is possible to generate H2 gas from H3O- in tissue in precise areas and to measure pancreatic regional blood flow easily, immediately, and steadily. Reliability and reproducibility were as good as for the H2 gas clearance method. Although the H2 gas clearance method has disadvantages in measuring pancreatic regional blood flow, especially in hypocirculation and in small animals, this new method can be used effectively. It will be useful in the investigation and examination of pathologic conditions in small animals and in humans.