Background: Administrative data sets are increasingly being used to describe clinical care in sickle cell disease (SCD). We recently used such an administrative database to look at the frequency of acute chest syndrome (ACS) and the use of transfusion to treat this syndrome in California patients from 2005 to 2010. Our results revealed a surprisingly low rate of transfusion for this life-threatening situation. Procedure: To validate these results, we compared California OSPHD (Office of Statewide Health Planning and Development) administrative data with medical record review of patients diagnosed with ACS identified by two pediatric and one adult hospital databases during 2009-2010. Results: ACS or a related pulmonary process accounted for one-fifth of the inpatient hospital discharges associated with the diagnosis of SCD between 2005 and 2010. Only 47% of those discharges were associated with a transfusion. However, chart reviews found that hospital databases over-reported visits for ACS. OSHPD underreported transfusions compared to hospital data. The net effect was a markedly higher true rate of transfusion (40.7% vs. 70.2%). Conclusions: These results point out the difficulties in using this administrative data base to describe clinical care for ACS given the variation in clinician recognition of this entity. OSPHD is widely used to inform health care policy in California and contributes to national databases. Our study suggests that using this administrative database to assess clinical care for SCD may lead to inaccurate assumptions about quality of care for SCD patients in California. Future studies on health services in SCD may require a different methodology. Pediatr Blood Cancer 2013;60:1936-1939. © 2013 Wiley Periodicals, Inc.