In 7 splenectomized and 21 non splenectomized pediatric patients with hereditary spherocytosis (HS), red cell size and hemoglobin concentration distribution (erythrograms) demonstrated the size and chromia degree of red cell populations. The H-1 Technicon graphic reports obtained in the analysis of HS blood showed a remarkable shift of the Hb concentration histograms to the right end of the x-axis, revealing the presence of a high percentage of hyperchromic red cells. The opposite shift was noted for volume histograms. Graphic findings were quantitated by a computerized program of the H-1 Technicon system. These data have enabled us to determine the percentage of microcytic and normocytic hyperchromic RBC. In particular, non splenectomized HS patients showed an increase in microcytic and hyperchromic RBC twice as high as that of splenectomized patients (data computed by erythrograms). Moreover, there is a significant difference (5.6%, p less than 0.01) between splenectomized and non splenectomized patients in the microcytic hyperchromic RBC percentage (data computed by special volume/hemoglobin concentration mapping).