Mutations of the p53 tumor suppressor gene can result in unregulated cellular growth and have been implicated in numerous malignancies. The aim of our study was to evaluate the prognostic significance of p53 protein immunoreactivity for prostate cancer and to determine whether p53 immunoreactivity correlates with the Gleason tumor grade in primary adenocarcinoma. Prostate fragments were fixed in 10% neutral-buffered-formalin, paraffinembedded, sectioned and standard Hematoxylin–Eosin stained, then examined using histological grade (Gleason system). P53 expression was studied using immunohistochemistry with monoclonal antibody anti-p53 mutant, 1 : 100 (DO-7) on tissue samples obtained during transurethral resection, in 40 patients with prostate carcinoma: Staining was defined as positive for p53 whenever any specific nuclear staining was detected. We considered tumors to overexpress p53 protein only when strong nuclear staining was present. lmmunoreactivity (IR) was categorized semi-quantitatively from 0 to 10% = negative, 11% to 40% weak, 41% to 70% moderate and 71% to 100% strong. 7 of 40 (17,5%) tumors are strong nuclear staining, 18 of 40 (45,0%) are moderate, 10 of 40 (25,0%) are weak and 5 of 40 (12,5%) are negative. Results were then compared to Gleason score. lmmunohistochemical detection of mutant p53 appears not to be an independent predictor of progression.