Abstract: In a method of measuring the specific activity of dehydrogenases by using a specimen prepared through a first procedure of causing dehydrogenases in tissue flake to be measured to be reacted with a substrate for a predetermined time and dyeing the same with tetrazolium salt and a second procedure of dyeing the protein in the flake with naphthol yellows, there is provided a third procedure of washing the enzyme-dyed flake with alcohol for a predetermined time after the first procedure. A specimen prepared through the first, second and third procedures is is microphotometered by the use of three predetermined wavelengths in the vicinity of 450 nm, 570 nm and 700 nm, and the specific activity of the dehydrogenases is measured from data obtained corresponding to the respective wavelengths.