LED (light emitting diode) technology has been developed rapidly in recent years in the area of illumination applications. However, the rate of heat generation increases with the LED illumination intensity. The LED chip temperature is critical to determine the LED lifetime and efficiency. In this study, the thermal conductivities of grease mixed with four different nanoparticles - MWCNT (multi-walled carbon nanotube), silver, copper (II) oxide, and aluminum oxide (Al2O3) are measured by using a solid thermal conductivity measurement system. It is found that the measured thermal conductivities of the grease with MWCNT, silver, copper (II) oxide, and aluminum oxide enhance up to 82.8, 26, 58.8 and 40% at 1.0 wt%, respectively, compared with that of the pure grease. Results confirm that the MWCNT grease is the best candidate out of the four different nanoparticles-based greases for the LED package cooling performance. (C) 2013 Elsevier Ltd. All rights reserved.