A supportive family environment is thought to enhance the capacity of cancer patients to adapt to their illness and treatment. But families, like patients, vary in their ability to cope with the impact of a cancer diagnosis in a family member and in their ability to fulfill the patient's needs. Increased understanding of the interrelationships between the family's and patient's responses to illness is of fundamental importance to the care of the patient with cancer. A heterogeneous sample of 201 cancer patients and their relatives were studied to determine compatibility of psychological status and to isolate clinical and demographic variables associated with psychological distress. Self-report tests of anxiety, mood disturbance, and mental health were applied. Despite large individual variation, the psychological status of patients and their matched relatives was closely correlated. The patient's treatment status affected both patients and their next-of-kin. Psychological well-being worsened according to whether patients were receiving follow-up care, active treatment, or palliative therapy. These data suggest a mutuality of psychological response between patients and their families. Supportive intervention for the patient or relative who manifests distress, therefore, should benefit both. Because patients and relatives involved with palliative treatment are most in need of psychological assistance, particular attention should be paid to this group, as is attempted in hospice care.