A cytochemical method of detection of dehydrogenases in blood leucocytes is proposed. Native smears are dried up in the air to be incubated at 37 degrees C in gel-containing medium composed of polyvinyl alcohol, sucrose, a corresponding substrate, cofactors and inhibitors of cytochrome oxidases activity. Using corresponding media, activities of succinate, malate, glutamate, lactate-, alpha-glycerophosphate, alcohol, beta-oxybutyrate and glucoso-5-phosphate dehydrogenases were revealed. Half-reduced diformazan providing diffuse rosy staining of cells was removed after the incubation, and the incubation medium was washed out by rinsing the smears in 60% acetone solution. As a result monochromatic micropreparations may be received. Finally, smears are fixed in formalin. The above method provides a reduced loss of enzymes, preserves a good cell morphology and eliminates non-dehydrogenase effects of tetrazolium reduction into formazan.