1. Department of Disease Prevention Chiyoda-ku Kojimachi Public Health Center 2-7-4 Hirakawa-cho, Chiyoda-ku Tokyo 102, Japan
2. Medical Information and Education Unit Department of Medical Information on AIDS National Medical Center Tokyo, Japan
3. Health Planning Division Health Policy Bureau Ministry of Health and Welfare Tokyo, Japan
4. Department of Public Health Jichi Medical School Tochigi-ken, Japan