Today, about 20 years after the discovery of cellular genes with oncogenic potential, we possess substantial knowledge on the regulation of normal cell growth and division. At the same time, we have gained insight into the loss of growth control which occurs in cancer cells. The following is a brief review of the progress made in oncogene research and the knowledge we have gained. It is important to stress that our understanding of the cellular and molecular mechanisms involved is still in its infancy. However, pieces are being added to the puzzle at an increasingly faster pace, primarily because of the progress in gene technology during the last two decades. Research methods have been set up to allow greater cooperation across disciplinary boundaries, thus increasing the speed with which important discoveries occur. A goal for the future will be to identify all oncogenes and tumor suppressor genes and elucidate their functions. At the same time, one of the major challenges will be to translate the knowledge thus gained into the development of more powerful and specific therapeutic strategies. As a result of the increasing insight gained by modern oncogene research, the need for detailed cancer diagnostics based on molecular genetics will increase significantly in the future.