Pilot and demonstration plants (PDPs) play important roles in technological development. They represent bridges between basic knowledge generation and technological breakthroughs on the one hand, and industrial application and commercial adoption on the other. The objectives of this article are to synthesise and categorise existing research on PDPs, as well as to suggest an agenda for future research. We review the PDP phenomena in three literature streams: engineering and natural science research, technology and innovation management, and innovation systems. The analysis highlights clear differences in e.g. conceptions of system boundaries and what the literature streams seeks to accomplish, but also similarities such as the key ideas of using PDPs for technology scale-up and uncertainty reduction.