Oncology nurses are becoming involved more frequently in answering questions regarding cancer prevention and detection. This article includes a discussion of basic underlying principles of cancer prevention and detection, including types of prevention, frequently used epidemiologic terms, validity assessments of cancer screening tests, and strategies for risk assessment. An understanding of basic principles related to cancer prevention and detection is necessary to provide information and patient education that is accurate and beneficial to patients and their families. With this background information, oncology nurses can help develop programs for cancer prevention and control.