Sickle cell disease (SCD) is an autosomal recessive disorder and the most common genetic disease affecting African-Americans. Approximately 0.15 percent of African-Americans are homozygous for sickle cell disease, and 8 percent have sickle cell trait. Acute pain crisis, acute chest syndrome (ACS), and pulmonary hypertension are common complications of sickle cell anemia. Pulmonary hypertension (PH) has now been identified as a marker of mortality in adults with sickle cell disease. Sildenafil has been proven beneficial in pulmonary hypertension (PH) and recent phase I/II studies from the intramural National Institutes of Health (NIH) suggest it is well tolerated and efficacious in the SCD population. Furthermore, a number of recent studies have suggested that nitric oxide (NO) based therapies may have a favorable impact on sickle red cells at the molecular level and could improve the abnormal microvascular perfusion that is characteristic of sickle cell anemia.