The medical records of all children at our hospital with International Classification of Diseases 9th revision (ICD-9) codes 342, 433 to 438, or 767 from May 1999 to May 2004 were reviewed to assess whether they had stroke (any type) or, specifically, arterial ischemic stroke (AIS). Code accuracy ranged from 37 to 88%; each code missed more than half of AIS identified by the combined code search. Studies are needed to determine whether other local and national ICD-9 databases have similar limitations.