Prostate cancer (prostate adenocarcinoma) has become an important concern in terms of public health these past fifteen years; recent French epidemiological data revealed 10,104 deaths due to this disease in 2000. The two main factors involved are the serum prostatic specific antigen (PSA), routinely used since late 1980's and which allows early diagnosis (before symptom onset), and the lengthened duration of life. Such cancer is rare before the age of 50, but its frequency increases with age, making it the most frequent type of cancer in French men. Although the aetiology of this disease is unknown, the ethnic origin, and a familial history of prostate or breast cancer are known risk factors. Predisposing genes to such hereditary types remain to be identified. Other genetic factors (polymorphisms), combined with environmental factors such as nutrition, have been incriminated, which is likely to explain the geographical variations of this affection. At the molecular level, the mechanisms involved in the tumoral initiation and progression remain unclear. Various genetic alterations have been identified among the genome of cancerous cells, at various stages of the affection: intraepithelial neoplasia, localized, locally advanced, metastatic or hormone refractory stage -, hormonal escape). However, the precise sequence and nature of the complex molecular events remain to be determined prior to their routine utilisation in the determination of subjects at risk, or as prognostic factors, and even as therapeutic targets. The anatomopathology is a key for the diagnosis. Intraepithelial neoplasia is the pre-cancerous lesion observed in most adenocarcinomas; these are localized in the peripheral part of the prostate gland in 70% of the cases. Gleason's classification is the current gold standard for the determination of tumoral aggressiveness and categorisation of the adenocarcinomas which are basically heterogeneous (coexistence of tumors cells with different degrees of differenciation in the same tumor). This anatomopathological classification allows distinguishing the tumours in terms of potential progressiveness and prognosis, and hence, to orientate the therapeutic strategy in case of localised or locally advanced prostate cancer.