The purpose of the study is to develop a Web-based health information service system for the middle-aged women. To identify users' information needs, we conducted an online survey of 189 middle-aged women. It was found that they had various health problems but very few did any health prevention or health promotion activities. We developed following contents in the following areas based on the result of needs assessment. They were exercise, diet including weight control, osteoporosis, climacteric, aging, breast and cervical cancer. Besides this health information, FAQ on women's health, my health knowledge test, statistics, link to related institutes and web sites, newspaper articles/mass media clips, journal articles, conferences papers, and other educational information were added. The homepage was developed as a subsystem of the Healthguide. It was evaluated by the users and the expert panel. The users rated 3.6 out of 5 point in their satisfaction rating and the experts rated 3.9 out of 5 in their site evaluation. It is expected that a Web-based women's health information service system will contribute to women's health promotion as well as provide a community for women's health related researchers and experts to share information on women's health.