In 1984, Peter Reichertz gave a lecture on the past, present and future of hospital information systems. In the meantime, there has been a tremendous progress in medicine as well as in informatics. One important benefit of this progress is that our life expectancy is nowadays significantly higher than it would have been even some few decades ago. This progress, leading to aging societies, is of influence to the organization of health care and to the future development of its information systems. Twenty years later, referring to Peter Reichertz' lecture, but now considering health information systems (HIS), two questions are discussed: which were lines of development in health information systems from the past until today? What are consequences for health information systems in the future? The following lines of development for HIS were considered as important: (1) the shift from paper-based to computer-based processing and storage, as well as the increase of data in health care settings; (2) the shift from institution-centered departmental and, later, hospital information systems towards regional and global HIS; (3) the inclusion of patients and health consumers as HIS users, besides health care professionals and administrators; (4) the use of HIS data not only for patient care and administrative purposes, but also for health care planning as well as clinical and epidemiological research; (5) the shift from focusing mainly on technical HIS problems to those of change management as well as of strategic information management; (6) the shift from mainly alpha-numeric data in HIS to images and now also to data on the molecular level; (7) the steady increase of new technologies to be included, now starting to include ubiquitous computing environments and sensor-based technologies for health monitoring. As consequences for HIS in the future, first the need for institutional and (inter-) national HIS-strategies is seen, second the need to explore new (transinstitutional) HIS architectural styles, third the need for education in health informatics and/or biomedical informatics, including appropriate knowledge and skills on HIS. As these new HIS are urgently needed for reorganizing health care in an aging society, as last consequence the need for research around HIS is seen. Research should include the development and investigation of appropriate transinstitutional information system architectures, of adequate methods for strategic information management, of methods for modeling and evaluating HIS, the development and investigation of comprehensive electronic patient records, providing appropriate access for health care professionals as well as for patients, in the broad sense as described here, e.g. including home care and health monitoring facilities. Comparing the world in 1984 and in 2004, we have to recognize that we imperceptibly, stepwise arrived at a new world. HIS have become one of the most challenging and promising fields of research, education and practice for medical informatics, with significant benefits to medicine and health care in general.