The health care system`s rapid transformation from one in which the hospital plays a major role to one in which the hospital is no longer central to the delivery of health care has had a tremendous impact on psychiatric nursing, In Korea, the community mental health system has just begun to take root. In these days, psychiatric nurse specialists have come to take an interest in rehabilitation, caring for the psychiatric patients, community mental health. However, the developmental state of the community mental health system is rudimentary and the studies which are supposed to restore the psychosocial function of the chronic mentally ill patients and insufficient. Following this requirement, this study was designed to test the effects of community-based mental health nursing program on self-care activities of mentally ill patients. The sample of this study consisted of 26 patients who were registered with certain health center in Seoul and attending this program. This study was conducted for 18 months from the beginning of Aug. 1996 to the end for Feb. of 1998. The program required a client`s meeting 5 times a week and family counsellor once a week, and was consisted of home visiting and day care program. Data by using Self-care performance scale were collected four times : right after participation, and in month six, and twelve, eighteen, and analyzed by the statistical methods of Repeated Measures ANOVA. The results of this study were as follows : 1. The was a significant difference in the scores of self-care activities of chronic mentally ill according to the duration of their participation in this program in all categories except eating and sleeping activities. 2. There was a statistically significant difference between before and the 6 months after the participation in the program in the eating, individual hygiene, dressing, leisure activities. At 12-month after participating the program, the subjects showed statistically significant improvement in all categories except sleeping, home life, leisure activities. Also, there was a statistically significant difference between before and 18-month after treatment in all categories expect eating and social life activities. 3. There was no significant difference in the score of self-care activities between 6-month and 12-month after participating program. Thus, both of patients and nursing care givers are apt to be tired of their work at these time. 4. At 18-month after the participation in this program, the scores of leisure activities, social activities were significantly different from those of 6-month and 12-month. In the light of these results, community-based mental health nursing program can improve self-care activities by helping them to continue their life and to function as a good support system for the chronic mentally ill. The researchers, therefore, propose that this program should be extended to the other place and be supported by local and central government.