Abstract: Histologic grade is a strong prognostic factor in prostatic adenocarcinoma. Since 1999, Gleason grading is the recognized international standard for prostate cancer grading and is now used routinely by most pathologists around the world. Problems with grading include interobserver variability, intraobserver variability, imprecise predictive value, and, since 2005, introduction of a competing modified system that advocates use without attribution as equivalent to classic Gleason grading. All grading systems successfully identify well-differentiated adenocarcinoma, which progresses slowly, and poorly differentiated adenocarcinoma, which progresses rapidly; however, they have difficulty subdividing the majority of moderately differentiated adenocarcinomas, which have intermediate clinical and biologic potential. In biopsies, these problems are compounded by small sample size, tumor heterogeneity and undergrading of biopsy samples. Also, significant histologic changes in adenocarcinoma occur as a result of radiation and androgen deprivation therapy. This review describes the current role of grading in prostatic adenocarcinoma, including reproducibility, possible improvements in grading such as the International Society of Urologic Pathology 2005 modified Gleason scoring system, correlation of biopsy grade with prostatectomy grade, the influence of treatment on adenocarcinoma grade, and correlation of grade with anatomic and biochemical markers of progression.