In an attempt to assess the reliability of a method for measurement of local blood flow-namely, the clearance of electrochemically generated hydrogen gas-a series of experiments were conducted using the skin and skin flap in rats and rabbits. The results showed high accuracy in obtained values, good reproducibility in the repeated measurements, and consistency with the values obtained by the hydrogen gas inhalation method. Histological examination revealed only minimal damage to the tissue resulting from the measurement. Using this method, blood flow was measured at different sites on the flap in rats. The critical point of blood flow as measured by this method was thoroughly consistent with the dye distance as well as with the survival length. No injurious effects of the measurement procedure on flap survival were noticed. The present study suggests a wide potential application of this method in plastic surgery because of its high reliability and because no radioactivity is involved.