OBJECTIVE High grade prostatic intraepithelial neoplasia is the most likely precursor of invasive prostate cancer. The identification of prostatic intraepithelial neoplasia in needle biopsy specimens warrants repeat biopsy because of its high predictive value for cancer. The incidence of prostatic intraepithelial neoplasia in contemporary needle biopsies is unknown. METHODS To determine the incidence of patients requiring repeat needle biopsy because of abnormal findings in needle aspirations (high grade prostatic intraepithelial neoplasia and microscopic foci suspicious for but not diagnostic of malignancy), we compared the pathological findings in 400 prostatic needle biopsies, including 200 consecutive cases from an academic medical center (Mayo Clinic) and an equal number from a private practice laboratory (Glendale Memorial Hospital and Health Center). RESULTS The biopsies revealed similar findings from the 2 medical centers: benign prostatic tissue in 41.5 to 50% of the cases, prostatic intraepithelial neoplasia in 16.5 to 9.5%, foci suspicious for but not diagnostic of malignancy in 1.5 to 2.5% and cancer in 40.5 to 38% (Mayo Clinic versus Glendale Memorial, respectively). Clinical information was available from the 200 Mayo Clinic patients who underwent biopsy, and there was no difference in the distribution of findings by digital rectal examination or transrectal ultrasound, although the median serum prostate specific antigen concentration was higher in patients with prostatic intraepithelial neoplasia and cancer than in those with benign biopsies. CONCLUSIONS High grade prostatic intraepithelial neoplasia is a frequent finding in needle biopsies and is present in up to 16.5% of the cases. There was no apparent difference in the incidence of prostatic intraepithelial neoplasia and cancer between 2 geographically diverse medical centers. Up to 18% of patients are candidates for another biopsy based on needle biopsy findings of prostatic intraepithelial neoplasia or foci suspicious for but not diagnostic of malignancy.