Long-term hospitalization is a problem for psychiatric care in Japan. The purpose of this research was to clarify the demands placed on public health nurses' (PHN) involved in the discharge of long-term inpatients (LIPs) with mental illness, and their lack of support. A questionnaire was mailed to 516 health centers, and 112 health centers replied. The response rate was 21.7 percent. The mail survey questionnaire was based on original questionnaire developed by the authors. Significant differences were found among collaborative agencies selected as essential for the discharge support project for the LIPs with mental illness. These differences were evident in the following question items on insufficiency of support: "Incompatibility with the policy of the public health center on discharge support"; "Opposition to discharge of a LIPs with mental illness by hospital staff"; and "Shortage of PHN in charge of the discharge support project for the LIPs with mental illness". It was clarified that the discharge support project required not only the involvement of health and medical welfare personnel but also the cooperation of local human resources such as local residents, neighbor associations, social workers, real-estate agencies and others.