Peak oil research and the Association for the Study of Peak Oil and Gas (ASPO) have contributed a great deal to improve people's recognition of peak oil. Although peak oil is becoming a part of public recognition, it is still hard to say whether peak oil discussion will develop into a theory such as "peakoilism". On one hand, there are still some difficult problems in peak oil research. On the other hand, the peakoilers have the potential for scientific research and have their allies: the climate change researchers and the new energy advocates. Oil is a limited, non-renewable resource, and an oil peak is inevitable. Peak oil theory is a kind of development theory rather than a crisis theory, which promotes reasonable utilization of the limited oil resources, promotes conservation, and encourages the development of renewable energy. (C) 2009 Elsevier Ltd. All rights reserved.