Worldwide populations are aging and countries have to prepare for the effects of demographic change in health care. Health information exchange (HIE), which is the process of moving patient information across health care providers electronically, can help overcome health data fragmentation and open opportunities to improve patient care in terms of quality, economy and efficiency. Since Japan and Germany are among the first countries strongly impacted by demographic changes of aging populations, we report on current developments about health information systems carrying out HIE based on case studies in both countries. Four projects that address the improvement of HIE within a defined region have been selected and investigated: the German project of the Lower Saxony Bank of Health and the Japanese projects Chiba ITnet, Nagasaki AjisaiNet and the National Disaster and Backup System of Japan. The project descriptions are based on relevant English publications, on-site visits and interviews with developers and users. The projects are introduced in terms of their basic architecture and implementation, their present status and future objectives. The projects' developments are still in progress and all have to cope with significant challenges before they will be able to provide a fully working trans-institutional health network solution.