Denial is a basic mechanism for coping with stressful themes, common in healthy and sick individuals. This article deals with the role and functions of denial in cancer, reviewing empirical studies about the effects of denial on cancer prevention, screening, undergoing tests for early detection, delay in seeking medical attention and getting treatment, complying with medical instructions, and coping with the disease in different stages. Special sections are devoted to the possible role of denial as a risk factor for cancer, the effects of denial on disease course and survival, and the relation of denial to immunocompetence. Major conclusions are that denial may have a positive effect when applied in the first phase of coping, after diagnosis, because it reduces anxiety. This holds also for the terminal stage. The negative effects of denial are that it may interfere with getting treatment (e.g., delay in going to the doctor, not showing up for follow-ups, noncompliance), may disrupt the process of assimilating the stressful event, may affect adversely interpersonal relations, and constitutes a cumulative stressor depressing even immunocompetence. The use of denial varies with the severity of the situation, the patient's personality, and his or her familial and cultural background. A large body of research examined the hypothesis that a tendency toward denial could be one of the risk factors for cancer. Despite evidence supporting the occurrence of denial as a correlate of cancer, a lot of research is necessary to clarify the role of denial in general and of anger specifically as a factor affecting the occurrence of cancer and the course of disease and survival.