Background:In patients with SCD, the spleen commonly enlarges during the first two decades of life but then undergoes autosplenectomy due to repeated attacks of vaso-occlusion and infarction. This, however, is not the case in Saudi patients with SCD, where splenomegaly sometimes persists into adult life. Patients and Methods: Ultrasonography was used to evaluate spleen size in 363 Saudi patients with SCD (340 SCD and 23 sickle ß-thalassemia). A total of 363 patients were evaluated. Their ages ranged from 1-60 years (mean 16 years). Results: Only 24 (6.6%) of our patients had autosplenectomy. The splenic index increased with age until about 40 years of age and then gradually decreased, indicating persistence of splenomegaly in our patients into an older age group. Forty-three patients (11.8%) had marked-massive splenomegaly (splenic index >120 cm) and these had higher HbF levels (mean HbF=22.2%) when compared with those who had autosplenectomy (mean HbF=14.6). This is significant (P-value=0.0169) and confirms the effect of HbF on persistence of splenomegaly in SCD patients. Conclusions: Ultrasonography is a simple, safe and accurate method of assessing splenic size in patients with sickle cell disease. Patients with persistent splenomegaly should be followed closely for development of complications which may necessitate splenectomy.