If multiple biopsy cores contain prostate cancer with differing Gleason scores, should an overall Gleason score be assigned, or should each core be graded separately? We obtained data on 127 men with prostate cancer on needle biopsy who underwent subsequent radical prostatectomy at our institution. We compared the Gleason scores found on needle biopsy with the grade and stage (organ-confined, extra-prostatic extension, positive seminal vesicles or lymph nodes) at radical prostatectomy. On biopsy, 40 men had a pure Gleason score of 4 + 3 = 7, 25 men had a Gleason score of 4 + 3 = 7 with a Gleason score of 3 + 3 = 6 on a separate core of the biopsy specimen, 27 men had a pure Gleason score of 4 + 4 = 8, and 35 men had a Gleason score of 4 + 4 = 8 with separate cores containing Gleason pattern grade 3. A Gleason score of 4 + 4 = 8 with pattern grade 3 in other cores had a more advanced stage than a pure Gleason score of 4 + 3 = 7 (P = 0.008). There was no clear pattern analyzing pathological stage of men with a pure Gleason score of 4 + 3 = 7 in comparison with those with Gleason scores of 4 + 3 = 7 and 3 + 3 = 6 in other cores. The group with a Gleason score of 4 + 4 = 8 and Gleason pattern grade 3 on other cores had a higher overall grade on radical prostatectomy than the group with a pure Gleason score of 4 + 3 = 7 (P = 0.001). If one had assigned an overall Gleason score, then a biopsy with Gleason score 4 + 4 = 8 on 1 or more cores and some pattern grade 3 in other cores, would be designated as a Gleason score of 4 + 3 = 7. Based on our findings, patients with a Gleason score of 4 + 4 = 8 on one or more cores with pattern grade 3 in other cores should be given a final Gleason score of 4 + 4 = 8 instead of 4 + 3 = 7, because these patients are more likely to have higher stage and grade on radical prostatectomy, comparable to a pure Gleason score of 4 + 4 = 8. Each core should be assigned a separate Gleason score, especially in cases with high Gleason score cancer on at least 1 core.