Red cell count is estimated with the use of a MKMF-1 microcolorimeter. 10 ml of Gower's solution are used; 0.02 ml of blood are added to this solution. Photometry of red cell suspension is carried out in a cuvette with a 0.5 cm optic route at lambda 610 nm. Microampermeter data are read from the optic density D scale. The D value is substituted into the formula: red cell count (RC) = K.D.10(6), where K coefficient is found experimentally by measuring the D and by estimating red cell count in microscopy, and is equal to 33.3. This formula permits estimating red cell count in 1 microliter of blood.