A number of genetic changes have been documented in prostate cancer, ranging from allelic loss to point mutations and changes in DNA methylation patterns. Up to now among the most consistent changes are those of allelic loss events, with the majority of tumours examined showing loss of alleles from at least one chromosomal arm. Chromosomes 8 and 13 appear to be the most frequently affected, with the former showing both loss of alleles from the short arm and gain of sequences on the long arm. Deletions of one copy of the RB gene are common, whereas deletion and/or point mutation of the TP53 gene is a less frequent event, at least in clinically localized tumours. Alterations in the E-cadherin/alpha catenin mediated cell-cell adhesion mechanism appear to be present in over one third of all prostate cancers and may be critical to the acquisition of metastatic potential of aggressive prostate cancers. In addition, altered DNA methylation patterns have been found in the majority of prostate cancers examined, suggesting an important role for methylation modulated gene expression in prostate carcinogenesis. Finally, the existence of prostate cancer susceptibility genes is suggested by study of familial clustering of prostate cancer, and it is expected that the identification of these genes will provide insight into critical rate limiting steps in the carcinogenic pathway of both inherited and sporadic disease.