This document is a guide developed for the measurement of high-power light emitting diodes (LEDs), normally in a form of LED packages, used for lighting products. High-power LEDs are those that require a heat sink for their normal operation. The light output of an LED depends strongly on its thermal conditions, in particular, the junction temperatures Tj. Junction temperature, however, is difficult to measure. Various different methods have been used to operate LEDs for photometric measurements and the results could not be compared. This document provides uniform test methods for operation of highpower LEDs and test methods for photometric and colorimetric measurement of high-power LEDs.