Mixing rods are used in illumination systems to provide a uniform output. The use of separate sources, especially RGB LEDs, has renewed interest in the use of mixing rods. This paper describes some of the special issues that arise with the use of RGB LEDs. Issues discussed include die layout for RGB LED arrays, straight round mixers with ripples and RGB LEDs, the use of a diffusers with mixers, and the use of a square to rectangular mixer with ripples to circularize the mixer's angular output.© (2008) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.