Physical therapists are frequently called upon to aid in the physical rehabilitation of cancer patients. They also share responsibility for the psychosocial aspects of care with other members of the treatment team. The objective of this paper is to provide guidelines to assist physical therapists in providing psychosocial support to cancer patients referred for therapy around the time of diagnosis or during the initial treatment period. Normal and pathological responses of patients faced with the diagnosis and treatment of cancer, including shock, fear, anger, anxiety and depression, are noted. Special attention is given to the importance of common defense mechanisms--denial, regression, rationalization and projection--and the difficulties faced by caregivers in dealing with these defenses. Principles of psychosocial intervention appropriate for use by physical therapists are presented. Two general types are suggested: the first concerns the patient's responses and feelings about the disease and the second involves educating the patient about how to most effectively deal with the disease. Physical therapists have an obligation to provide more than physical restorative services for cancer patients; they should be able to offer psychosocial support in an effort to enhance successful rehabilitation and reintegration to normal living patterns.