Multiple studies have demonstrated discrepancy rates between original and review histopathologic diagnoses of up to 30% with a mean of approximately 10%. In view of these rates of discrepancy, several authorities, including the Association of Directors of Anatomic and Surgical Pathology, have recommended in-house review of all outside materials before commencement of therapy. We used a mail survey to determine the degree of compliance with these recommendations among pathology groups in the United States. Mail surveys were sent to six randomly selected hospitals from each state (300 total). The survey included demographic questions, including surgical pathology caseload, size of hospital (beds), and type of hospital (community-general, non-academic-tertiary care, or academic-tertiary care). The survey asked whether the hospital required review of all outside slides before the performance of surgery. If not, was such a policy encouraged but not required. The survey also asked whether in-house review of outside cases had disclosed any significant differences in pathologic diagnoses. Finally, the survey questioned whether any discrepancies between an internal and external surgical pathology diagnosis had been discovered following radical surgery. One hundred twenty-six usable responses were obtained. Fifty-five of these were from hospitals self-described as community-general, seven were from hospitals describing themselves as non-academic-tertiary care, and the remaining 61 hospitals described themselves as academic-tertiary care institutions. Sixty-three institutions stated they had a requirement for in-house review of outside material, with 46 of 61 academic-tertiary centers having such a requirement. Thirty-seven of 55 community-general hospitals did not require in-house review of outside material before surgery could be performed. One hundred ten of the 126 institutions returning surveys either encouraged or required review of outside material. Ninety-five institutions reported that they had at least one outside case in which their diagnosis was significantly discordant with that rendered by the referring pathologist. Sixty (48%) of the 126 institutions reported at least one case in which a discrepancy was found between the outside biopsy diagnosis and the internal diagnosis rendered on material obtained by radical surgery. Approximately half of all responding institutions have a requirement for in-house review of outside material prior to surgery. A majority of institutions requiring such review have found discrepancies between the in-house diagnoses and those rendered by referring laboratories.