This study used a novel screening method to characterize the epidemiology of diagnostic errors in primary care. An electronic medical record was screened for hospitalizations or urgent visits occurring within 10 days following a primary care visit for the same symptoms. In more than 10% of these cases, the initial evaluating physician missed the diagnosis or arrived at an incorrect diagnosis, most commonly due to failure to take an adequate history. A prior study used comparable methods to identify a strikingly similar incidence of missed diagnosis of acute myocardial ischemia in the primary care setting.