The histopathological diagnosis is the bedrock of modern oncology, and plays a major role in the treatment of many other types of disease. Errors in these reports can critically affect patient care and may become the subject of media concern. This article considers how audit in histopathology can provide information about errors and inconsistencies in the diagnosis of surgical specimens. The use of audit to generate information about the background level of errors in pathology reports is reviewed, along with findings about the nature of these errors and the types of specimens more commonly affected. Generic audit strategies that can be used to minimize the risk of errors in reports are discussed, together with the use of audit to evaluate diagnostic criteria and pathological scoring or grading systems. The role of audit in determining the informational content of reports is included, and there is consideration of the relationship between sample size and error rates. The limited extent to which audit can be used to assess the performance of individual pathologists is also covered.