THE CLINICAL manifestations of sickle cell anemia are thought to be due to the abnormal hemoglobin in the erythrocytes. In addition to Hemoglobin S, however, the erythrocytes of patients with sickle cell anemia may also contain fetal hemoglobin.1 Since sickling of erythrocytes is decreased by fetal hemoglobin,2 this study was undertaken to evaluate the effect of persistence of significant amounts of fetal hemoglobin on the clinical severity of the manifestations of sickle cell anemia. Materials and Methods Hemoglobin electrophoresis was performed on the red cell hemolysates of all University of Mississippi Medical Center patients suspected of having sickle cell anemia or trait. The filter paper electrophoresis technique of Motulsky et al.3 was used. This method was modified by decreasing the voltage from 260 to 120 and increasing the duration of electrophoresis run from 5 to 23 hours, thereby achieving a greater spread of resulting components. Fetal