Nowadays the demand for thermal standards for power LEDs is increasing. On one hand metrics for fair comparison of competing products are needed; on the other hand, designers of power LED-based applications need reliable and meaningful data for their daily work. Today's data sheet information does hardly meet any of these requirements. In 2008 the JEDEC JC15 committee on thermal standardization of semiconductor devices decided to take action and created a task group to deal with thermal standardization issues of power LEDs. CIE has also created two new technical committees (TC2-63, TC2-64) which also aim to address thermal issues during measurement of high brightness / high power LEDs. This paper deals with thermal issues that are specific to light emitting diodes by describing novel test methods which may form basis of new measurement guidelines or standards including combined thermal and radiometric measurement of LEDs. Thermal issues in connection with short pulse measurements of LEDs and some thermal aspects of LM80 tests are also discussed.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.