We conducted a retrospective study of 262 malpractice claims against emergency physicians insured in Massachusetts by the state-mandated insurance carrier; these 262 claims were closed in the years 1980 through 1987. A total of $11,800,156 in indemnity and expenses was spent for these 262 claims. In 211 cases, the allegation was failure to diagnose a medical or surgical problem. One hundred eighty-four of these cases were included in the following eight diagnostic categories: chest pain, abdominal pain, wounds, fractures, pediatric fever/meningitis, aortic aneurysm, central nervous system bleeding, and epiglottitis. These eight categories accounted for 66.44% of the total dollars spent for the 262 claims. Because of the high incidence and dollar losses attached to these eight diagnostic categories, the Massachusetts Chapter of the American College of Emergency Physicians (MACEP) has developed clinical guidelines for the evaluation of these high-risk areas. Of the 184 high-risk claims, 99 claim files were reviewed; 45 of these reviewed claims were judged by physician reviewers as preventable by the application of the MACEP high risk clinical guidelines. From 22.26% to 46.4% of the $11,800,156 spent on the 262 claims could have been saved by the application of the MACEP clinical guidelines.