Investors have been showing interest in prospects for new environmental technologies launched by innovative enterprises. We analyse the experience of young environmental technology firms going public on London’s alternative stock market, AiM. While firms that launched in the boom attracted needed funds, shareholder expectations and the controls used to promote shareholder value were not well aligned with the realities of business development of these emerging technology firms. These face challenging market and technology risks and require funding for business development that is more flexible and longer term than that provided by AiM investors. We suggest that a wider portfolio of investment alternatives is needed