Despite its high incidence and mortality rate, the molecular mechanisms underlying the oncogenesis and progression of prostate cancer are still unclear. This review, based on recently published data, surveys the current state of knowledge of human prostate oncogenesis, dealing with genetic predisposition in familial clusters of prostate cancer, providing new information on the somatic genetic alterations, which have been approached in four ways (measurement of DNA content, cytogenetic analysis, in situ hybridization, and molecular analysis), and investigating the problems of androgen independence and intratumour heterogeneity in prostate tumours. Lastly, the potential clinical applications of the genetic alterations, which may become important in the near future, are addressed.