This paper aims to analyze how introduction of co-insurance for health care for the elderly in 2002 affects doctor-patient relationship with a qualitative study. Ten homebound old persons with frailty were interviewed using unstructured interview schedule. The interviews revealed that interviewees had become more cost-conscious and more concerned with cost-effectiveness of health care after the introduction of co-insurance. They felt that doctors and other health professionals did not provide enough information on costs of health care, which were likely to erode trust between physicians and patients. Despite recent efforts to improve communication skill in the health sector, policies of enhancing financial incentives on physicians' behavior and strengthening for-profit ethos in the health sector might disturb the doctor-patient relationship. Both micro- and macro-level efforts to build up trust are needed.