OBJECTIVES--To assess histopathologists' ability to accurately diagnose bronchopneumonia, both on naked eye and microscopic examination; to extrapolate from the error rate to determine whether the role of the necropsy in monitoring the epidemiology of clinical error might be compromised. METHODS--Review of archival histological sections and necropsy reports from two teaching hospitals in Manchester. The main outcome measures identified were the proportions of macroscopic diagnoses of bronchopneumonia which were confirmed by the original pathologist on histological examination, and which could be confirmed on histological review by independent pathologists, together with the proportion of discrepant diagnoses remedied in the final report by the original pathologist. RESULTS--Of 279 cases where a macroscopic diagnosis of bronchopneumonia had been noted in the original provisional necropsy report, the original histopathologist described bronchopneumonia in only 206 (73.8%) in the subsequent final report, which took histology into account. Bronchopneumonia could be confirmed on independent histological review in only 193 (69.2%) of these cases. The original histopathologist diagnosed 74 cases of bronchopneumonia on histological grounds only, of which only 57 (77.0%) could be confirmed on review. Of a total of 160 discrepancies between the original naked eye diagnoses and the final reviewed diagnoses, only 130 (81.3%) had been remedied by the original pathologist. CONCLUSIONS--There is a considerable discrepancy rate between naked eye diagnoses of bronchopneumonia at necropsy and diagnoses confirmed on microscopy. If this discrepancy rate is extrapolated to other common lesions, then the role of the necropsy in clinical audit may be compromised. Pathologists need to take steps to monitor and improve their own diagnostic standards.