Molecular biology has proven to be instrumental in studies on the onset and progression of cancer. Reasoning that tumorigenesis can be considered as a multistep process in which a normal cell gradually escapes from its delicately regulated growth pattern, one might describe this process in terms of gene expression. The group of genes that are good candidates for investigation in this context are the proto-oncogenes. Recent progress in oncogene research, has led us to believe that the group of oncogenes is much greater in number than the fifty so far characterized, since all growth factor-, growth factor receptor-, signal transducer- and transcription regulating genes have a potency to become oncogenic. Recessive genes, such as tumor suppressor genes might be equally relevant to the onset and progression of cancer. In this paper we confine ourselves to the role of protooncogenes in urological cancers, in particular prostate cancer. The usefulness of these genes as markers of progression in prostate cancer will be discussed.