Dramatic advances have been made in cancer treatment in recent years, enabling patients to leave the hospital more quickly and stay home while still undergoing treatment. As a result, the percentage of outpatients has been on the rise. Healthcare providers engaged in actual outpatient treatment, however, spend so much energy implementing daily procedures safely that they have little time remaining to provide patient education or carry out any other systematic patient support programs. Although self-care generally is believed to be what people do to help themselves, differences exist between Western countries and Japan in the interpretation of self-care. In Japan, obtaining necessary support from the family and friends that one relies on also is viewed as essential. Patients' self-care agency must be assessed if nurses are to make the most of patients' abilities; however, evaluation criteria for that purpose have yet to be established. Development of a method for evaluating the self-care agency of patients receiving chemotherapy on an outpatient basis is needed to ensure further advancement in this area of nursing.