Our aim was to study the level of interobserver concordance in the Gleason scores of prostate needle biopsy specimens reported at 1 institution. A retrospective review of all prostate needle biopsy specimens in which a diagnosis of adenocarcinoma was made during the year 2000 was conducted. Parameters evaluated included the Gleason score, Gleason grades identified, the percentage of Gleason grades 4 and 5, and the percentage of tumor in the biopsy specimen. Our results demonstrated a 60% overall concordance in consensus Gleason scores, which increased to 80% when considered in groups of a Gleason score of less than 7 vs 7 or more. The greatest discordance seemed to be in distinguishing Gleason score 6 from 7 and was more frequent among biopsy specimens with lower tumor volumes, particularly among those with less than 30% involvement. A small percentage of Gleason grade 4 pattern might predict disagreement as well. Strategies for improving accuracy of Gleason score 7 should be devised, and consensus diagnosis for biopsy specimens that demonstrate a low percentage of tumor volume is recommended.