The main objective of this project is to serve as the Statistical Coordinating Center for the Investigation of Selected Patient Groups from the Cooperative Study of Sickle Cell Disease (CSSCD). Specifically, the purpose is to provide statistical support, data management, coordination and leadership for the clinical centers involved in the investigation. The purpose of the over-all investigation is to continue to follow two important groups of patients from the previous phase of this collaborative study. The CSSCD has been a multi-institutional cooperative study investigating the clinical course or natural history of sickle cell disease from birth to death. The investigation has involved the enrollment and follow-up of approximately 4,000 patients. The present investigation, however, involves only two patient groups selected for further study, the newborn cohort of patients entered before the age of six months, and the adult cohort of patients over 35 years of age. The newborn cohort has approximately 650 children currently being followed in the clinical centers ranging in age from 2 months to 10 years. There are 473 adults over 35 years of age with the oldest patient being 74 years old.