Abstract: An informational text for practitioners in psychology, psychiatry, health administration/education, medicine, nursing, and other health support services involved in providing a comprehensive system of health care to patients collates and discusses current information concerning the effect of life-style and psychological and behavioral factors on the development of cancer. The text examines behavioral factors that can influence cancer development, ranging from enhanced risks to the effectiveness of treatment. Scientific evidence is summarized on behavioral and exposure risk factors, the biology of malignant tumors, the effectiveness of various cancer screening techniques, and the effect of confounding factors (e.g., patient compliance) on the effectiveness cancer treatments. Epidemiological research summaries, case studies, and clinician-patient interviews are included.