Sickle cell anemia is a complex syndrome with multiple organ system disturbances brought about by the interplay of genetic, humoral, vascular and environmental factors. The clinical course can be one of abrupt and insidious exacerbations and remissions, often migratory and repetitive. These events may result in impairment of function, permanently damaged organs, and ultimately death. Although there is wide variability in the clinical expression of sickle cell disease, this complex set of clinical manifestations is experienced by most patients. In addition, there is no evidence that the primary disease process is different in children when compared with adults with regard to painful episodes. However, children have a higher incidence of respiratory viral infections, and are susceptible to pneumococcal septicemia. With the successful completion of the Multicenter Study of Hydroxyurea (MSH) Trial in adults, attention has now been focused on the use of this agent in children.