Knowledge gained from the Human Genome Project and related genetic research is already impacting clinical oncology nursing practice. Because cancer is now understood to be a genetic disease, changes in the traditional approaches to prevention, diagnosis, and therapeutic management of cancer are becoming increasingly genetically based. Therefore, to ensure competency in oncology nursing practice at all levels, nurses must incorporate an understanding of the underlying biology of carcinogenesis and the molecular rationale underlying strategies to prevent, diagnose, and treat cancer.