In 296 patients with homozygous sickle cell disease (HbSS) detected during the screening of 100,000 deliveries between 1973-1981, chronic hypersplenism defined as a spleen measuring ≥4 cm below the costal margin with evidence of prolonged red cell sequestration occurred in 30 (10.1%) subjects, 23 resolved by splenectomy and 7 resolved spontaneously. Median age at splenectomy was 4.8 years and following splenectomy, median values for hemoglobin increased by 2.3 g/dL, reticulocytes fell by 8.3%, total nucleated cells fell by 2.2%, and platelets increased by 29,813 × 10