Nearly 43% of African American adults and 53-70% of African American adolescents in the US have vitamin D deficiency (VDD), ten times more than is seen in Caucasians. VDD is also quite common in sickle cell disease (SCD) with prevalence rates of 65-100%. Pain is a hallmark symptoms of SCD accounting for the majority of SCD morbidity. Some patients with SCD develop debilitating chronic pain with an unclear etiology and unsatisfactory response to treatment. Both VDD and SCD can cause chronic pain, compression fractures and myopathy. We hypothesize that VDD is implicated in the poor musculoskeletal health and chronic pain of SCD. Therefore we aim [1] to demonstrate that pediatric sickle cell patients have high rates of VDD and those with chronic pain have lower levels of vitamin D compared to those without chronic pain [2] to evaluate the musculoskeletal health, pain status, opioid analgesic use, depression and quality of life in SCD patients with and without chronic pain and determine if the presence or severity of VDD is associated with a more severe clinical phenotype and [3] to demonstrate that administration of replacement doses of vitamin D will correct VDD, improve musculoskeletal health and ameliorate chronic pain. An additional aim of this project is to [4] evaluate and describe any correlates between vitamin D status and serum levels of inflammatory cytokines, markers of oxidative stress and vitamin D receptor polymorphisms in SCD patients with and without chronic pain.