Objectives. To determine the incidence and clinical significance of high-grade prostatic intraepithelial neoplasia (PIN) in specimens obtained from transurethral resection of the prostate (TURF). Methods. AII TURF specimens accessioned to the general surgical pathology service of the Johns Hopkins Hospital (JHH) from March 1984 through December 1987 that did not contain adenocarcinoma of the prostate were reviewed for the presence of high-grade PIN (PIN 2 and PIN 3). These cases were supplemented with cases from the consultation files of the JHH, the Armed Forces Institute of Pathology, and the University of Michigan Hospitals. In total, 85 cases of high-grade PIN in TURF specimens were identified. Results, The mean age of the patients at the time of TURF was 70 years and the median age was 71 years (range 50 to 89). Sixty-three patients (74%) were 65 years of age or older, 45 patients (53%) were at least 70 years of age, and 14 patients (16%) were 60 years of age or younger. Adenocarcinoma of the prostate was discovered in 9 (22%) of 41 patients with follow-up information. Based on material from JHH, the incidence of high-grade PIN was 2.3% in all TURF specimens and 3.2% in those without invasive carcinoma. Conclusions, High-grade PIN on TURF is relatively uncommon and is diagnosed in an elderly population, Patients with high-grade PIN on TURF appear to be at increased risk of developing prostatic carcinoma, although not to the same degree as patients with high-grade PIN on needle biopsy. (C) 1997, Elsevier Science Inc.