"In this paper, we carry out a literature review of the studies investigating the factors that affect the performance and growth of clean technology start-up firms. The importance of clean-tech start-ups lies in their mission to protect the environment by facilitating the increased use of clean energy and environmentally friendly solutions. At the same time, the entrepreneurial nature of many of these firms enables introduction of radical innovations necessary for making breakthroughs in the industries of renewable energy and environmental technology that in turn are essential for the industry development. Given their significance, there are surprisingly few studies with the focus on the factors affecting the growth of clean-tech start-ups. Our search in leading management, entrepreneurship and energy journals has yielded a total of 13 articles, almost all of which focus on such external factors as policies. We argue that this gives us an incomplete picture of the factors enabling a clean-tech firm's development. As clean-tech firms are a subset of the population of new technology-based firms (NTBFs), we draw on the literature dealing with the factors that promote growth of NTBFs in order to build our framework for structuring the results. The analysis uncovers what future research areas can be pursued in order to gain a more balanced understanding of what enables the development of a clean-tech start-up. We suggest that in addition to the macro-studies of policies and regulations, future research needs to examine the individual and firm-specific factors, e.g. characteristics of the clean-tech entrepreneurs, teams, governance mechanisms and network structures. Furthermore, the existing focus on the environmental and innovative performance of clean-tech start-ups should be complemented by examining the alternative firm outcomes related to e.g. financial performance, social identity, alliance portfolio and internationalization."