The authors review the psychiatric symptoms that may precede, accompany, and follow the onset of cancer. Difficulty in expressing anxiety, depression, or anger and low scores on these parameters in psychological testing along with depression and feelings of hopelessness are linked with the emergence of malignant tumors. Cancers of the brain, pancreas, and other endocrine organs, and hormone-secreting tumors frequently develop following the appearance of psychiatric symptoms. The psychological adjustment of cancer patients and the more common psychiatric sequelae of malignancy and its treatment are examined. The authors emphasize the need for careful assessment and attention to the biologic, psychological, and social factors critical to the patient's response and adjustment to the disease.