Background: Acute and chronic clinical manifestations of sickle-cell disease (SCD) lead to significant healthcare utilization, especially of the emergency department (ED). Limited population-level data are available in SCD with the ability to connect patients to visits, leaving us with minimal description of utilization patterns.Procedure: Using ED discharge data with links between patients and visits, we sought to describe the California SCD population and its ED utilization patterns across facilities. Non-public California Office of Statewide Health Planning and Development data employ unique patient identifiers, linking patients, and visits.Results: SCD patients of all ages are heavily reliant on Medicaid (46%). The majority of SCD Californians visit an ED more than once during a year (69%), but only a minority use more than one facility during a year (34%). However, adults with SCD have multiple visits and utilize multiple EDs in higher proportions than do children (72% vs. 60% and 40% vs. 21%, respectively). A higher proportion of visits to the ED are made by SCD adults, but a higher proportion of visits by children result in hospital admission. Uninsured adults outnumber uninsured children (16% vs. 5%).Conclusions: ED utilization by the California SCD population is described on a population level. Utilization patterns by adults point towards increased utilization in the population no longer eligible for Title V pediatric coverage for their disease. Further investigation using population-level socioeconomic and geographic correlates is warranted to evaluate the factors leading to ED utilization in SCD. © 2010 Wiley-Liss, Inc.