This retrospective study identified patients presenting toan integrated health care delivery system’s ED with dizzinessand vertigo (International Classification of Diseases, 9th Revision[ICD–9] codes 386.11 and 780.4) between January 2008 and January2011. Only patients assigned to the health system’s healthmaintenance organization (HMO) were included in the study soas to allow access to all billable claims referable to the ED visitfor dizziness and subsequent clinical data