This paper elaborates on the general properties of medical innovation processes. It begins with a critical review of different perspectives and methods of investigation used in various streams of research that have previously analysed technical change in the health sector. After profiling and discussing their characteristics, the paper proposes an evolutionary approach
to change in medicine constructed around the notion of a ?Health Innovation System?. Health innovation, it is argued, consists of complex bundles of new medical technologies and clinical services emerging from a highly distributed competence base. Health Innovation Systems are driven by the combination of (1) institutionally-bound interactions among agents (?gateways? of innovation)
and (2) history-dependent trajectories of change (?pathways? of innovation) whose developments emerge from and feed back into the structure of the system through organised transfers of knowledge between research and clinical practice. After drawing examples from recent empirical work on clinical research in specific disease areas, the paper concludes by identifying implications
for further research.