Nanofluid is a new kind of working fluid with special properties to enhance the heat transfer of heat pipes. This paper reviews and summarizes the research done on heat pipes using nanofluids as working fluids in recent years. The effect of characteristics and mass concentrations of nanoparticles on the thermal performance in various kinds of heat pipes with different base fluids under various operating conditions have been discussed. The mechanism of enhancement or degradation of heat transfer utilizing nanofluids in the investigated heat pipes has been explained. The paper discusses the relative reduction of the total heat resistance for various heat pipes with nanofluids in comparison with the existing ones and also presents a perspective on possible future research applications. (C) 2012 Elsevier Ltd. All rights reserved.