The continuing decline in the performance of autopsies has led to considerable concern that physicians are increasingly unaware of diagnostic errors. Missed diagnoses may also adversely affect the accuracy of prognostic systems. This Swedish study compared hospital discharge data and autopsy data for trauma patients and found that missed injuries were relatively common despite an autopsy rate of less than 25%. The performance of the International Classification of Diseases Injury Severity Score—a commonly used prognostic tool for trauma patients—could have been improved by incorporating autopsy data. As in prior studies, the authors conclude that maintaining a high autopsy rate is essential to improving the accuracy of clinical diagnoses.