Blinded review has been shown to be an excellent method to detect disagreements and errors and improve performance in gynecologic cytology. Preliminary studies suggest it may be valuable in surgical pathology. We reviewed 5,000 sequential outpatient surgical pathology biopsy cases without knowledge of the original diagnosis or history and compared the results with those of the original diagnosis. Complete agreement was obtained in 91.12% of cases. The technique of blinded review of surgical pathology biopsy material had a sensitivity of more than 99%, failing to identify an abnormality in 19 cases. Although there was a significant level of diagnostic disagreement (444 cases), primarily due to differences in diagnostic thresholds (292 cases), diagnoses that resulted in a change in the original report (true errors) were present in only 5 cases, and only 4 were clinically significant. This clinically significant error rate of 0.08% is significantly lower than previously published error rates. Blinded review is a sensitive (99%) and effective method to identify areas of disagreement and errors in surgical pathology biopsy material. The relatively high rate of disagreement found with blinded review coupled with the very low rate of error highlights the substantial potential for bias in nonblinded reviews.