Pilot and demonstration plants (PDPs) play important roles in the process of technological development because they represent the bridge between basic knowledge generation and technological breakthroughs on the one hand, and industrial application and commercial adoption on the other. The objectives of this paper are to synthesize and categorize the existing research on PDPs, as well as to suggest an agenda for future research efforts. 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 in 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. These results are discussed and a future research agenda is provided.