In this report we rate a new, third-generation automated hematology system (Technicon Instruments H-1) that can furnish a full range of values, including erythrocyte parameters and a leukocyte differential count. Particular attention is focused on erythrocyte morphometric parameters, including measurement of cell size and hemoglobin content on a cell-by-cell basis. We assess the usefulness of new parameters derived from these measurements, such as mean corpuscular volume and red blood cell distribution width, which characterize cell size, and mean corpuscular hemoglobin concentration, and hemoglobin distribution width, which characterize cell hemoglobinization in evaluating normal and abnormal subjects. The value of these parameters in classifying anemias is assessed in our patient population that includes those with iron deficiency anemias and thalassemias, as well as other forms of anemia.