This study reviewed 549 malpractice claims filed against emergency physicians in Massachusetts from 1975 through 1993, with a total of $39,168,891 of indemnity and expense spent on the 549 closed claims. High-risk diagnostic categories (chest pain, abdominal pain, wounds, fractures, pediatric fever/meningitis, epiglottitis, central nervous system bleeding, and abdominal aortic aneurysm) accounted for 63.75% of all closed claims and 64.23% of the total indemnity and expense spent on closed claims. Missed myocardial infarction (chest pain) claims accounted for 25.47% of the total cost of closed claims but only 10.38% of closed claims. The number of claims for missed myocardial infarction increased in the post-1988 closed claim group compared to the pre-1988 group; fractures and wounds were significantly less frequent in the post-1988 group. The frequency of high-risk claims decreased in the post-1988 group, largely because of the decline in fracture and wound claims. The category of missed myocardial infarction had a larger percentage of claims closed with indemnity payment than without indemnity payment. This parameter may serve as a marker for the overall seriousness of claims associated with a particular allegation, unlike the average cost per claim, which may be skewed by a few large awards.