The proposed research is designed to investigate the utility of continuous, long-term PDE 5 inhibitor therapy as an intervention for recurrent ischemic priapism, a disorder of non-willful, excessive penile erection, in patients with SCD. Although precise prevalence figures are not available, priapism in SCD is highly prevalent and thought to afflict approximately 40% of males, based on available literature. Additionally, the disorder exacts devastating consequences, including erectile tissue necrosis, erectile dysfunction, and psychological distress. Management of this disorder remains challenging because the mechanisms underlying priapism are incompletely understood.