This study aims to show the effectiveness of hydroxyl urea in the treatment of severe forms of sickle-cell anemia. The study included 30 patients from patients with sickle cell anemia and who reviewed the Blood clinics in AL- Assad University Hospital . We had studied patients treated with hydroxy urea for at least 6 months, where it was compared to blood and clinical variables before and after hydroxy urea treatment. The results showed an improvement in blood and clinical manifestations , and it was noted a significant increase in the level of fetal hemoglobin, and a decrease in the level of hemoglobin and sickle cell after hydroxy urea treatment. hydroxy urea treatment also led to a clear increase in the level of total hemoglobin, and a decrease in the value of total bilirubin. Decrease in the number of the pain episodes that needed hospitalization, and the number of times of blood transfusion after treatment, too.