Because being diagnosed with cancer is considered to be extremely stressful, cancer patients' mental adjustment has been widely studied. Previous studies have revealed that cancer patients' mental adjustment is correlated with the quality of life and the degree of psychological distress and have suggested that one of the most adaptive adjustments is 'fighting spirit' whereas one of the most maladaptive is 'helplessness/hopelessness'. However, little is known about the association between patients' mental adjustment to cancer and their spouses characteristics or social support network. This paper describes a study of cancer patients' characteristics and social support factors as predictors of the patients' responses to having cancer. A total of 455 ambulatory cancer patients completed the Mental Adjustment to Cancer (MAC) scale and participated in a structured interview about their characteristics and social support. The results of multiple regression analysis suggested that size of household, performance status, support from physicians and satisfaction with support were predictive of patients' fighting spirit, whereas age, education, size of household, performance status and satisfaction with support were predictive of helplessness/hopelessness.