Аннотация:A new algorithm for measuring the width of erythrocyte size distribution based on the analysis of the diffractionpattern occurring in the far zone during the scattering of the laser beam on a blood smear is proposed. Thealgorithm is applicable to the analysis of weakly heterogeneous blood samples with symmetric size distributionfunction. The input data for the algorithm are the characteristics of the angular distribution of light intensity nearthe first dark ring in the diffraction pattern. The peculiarity of the algorithm is the reduced sensitivity to diffractionpattern noise, which is important for its experimental realization