Acinar carcinoma of the prostate is the third most frequently registered cancer and its incidence is expected to increase as life expectancy increases. Consequently, there have been attempts to introduce possible screening programmes for early detection of prostatic carcinoma. In this context the histopathologist has a role in that potential pre-neoplastic lesions have to be recognized. Two such pre-neoplastic lesions in the prostate are adenomatous hyperplasia and prostatic intraepithelial neoplasia. In this article the histological features of these lesions, their differential diagnosis and their pre-malignant potential are reviewed.