By inhibiting inflammation and several common pathways leading to vascular damage,simvastatin may help prevent the acute and chronic complications of SCD. The objective of this study is to determine whether our preliminary results showing simvastatin-associated reductions in plasma markers of vascular injury will translate into a reduction in vaso-occlusive pain episodes in patients with SCD. A web-based, smartphone-accessible electronic pain diary will be used to monitor frequency and intensity of vaso-occlusive pain in SCD patients treated with a single daily dose of simvastatin.