The role of intellectual property rights (IPRs) in the transfer of climate change technologies has emerged as a particularly contentious issue in the past two years. Against this background, the United Nations Environment Programme (UNEP), the European Patent Office (EPO) and the International Centre for Trade and Sustainable Development (ICTSD) joined forces to undertake an empirical study on the role of patents in the transfer of clean energy technologies (CETs). The project consisted of three main parts: a technology-mapping study of key CETs, a patent landscape based on the identified CETs and a survey of licensing practices. For the purposes of this study, CETs are energy generation technologies which have the potential for reducing greenhouse gas emissions.