The incidence of clinical prostate cancer varies across countries and ethnic groups. Genetic and epigenetic factors have been suggested as possible explanations to these variations, although no mesological factors with clearly significant effects have been identified. About 20% of patients with prostate cancer have a family history for this disease. Several studies have reported links between prostate cancer and breast cancer, suggesting that the same loci may predispose to both diseases. Identification of one or more inherited genes associated with an increased risk of prostate cancer in some families may be useful for identifying high-risk individuals. The value of this approach has been demonstrated in other familial cancers, such as colon and breast cancer. Current goals of research in this field are to localize the gene(s) that predispose to familial prostate cancer and to identify the molecular alterations related to tumor progression in sporadic and familial prostate cancer.