In the last few years, rare earth materials (REM) prices have experienced a strong increase due to geopolitical and sustainability issues. Financial markets could already have factored in concerns about shortages of REM supplies into clean energy companies' valuations. We use a multifactor market model for the period January 2006 to September 2012 to analyze the impact of REM price trends - specifically dysprosium and neodymium - on six clean energy indices (NYSE-BNEF) tracking the world's most important companies in the clean energy sector. The results show that during period of price increase, there is a negative relationships between REM price changes and the stock market performance of some clean energy indices. The European clean energy index is also negatively affected, and this effect could be relevant to policy makers, considering that Europe is implementing some relevant policy actions to support the development of the clean energy industry. (C) 2013 Elsevier Ltd. All rights reserved.