The thermal design of an LED fixture affects its light output, efficiency, cost, lifetime and reliability. LED based fixture designers and managers who are concerned about any of the above lighting fixture parameters are highly recommended to consider the practical simple concepts outlined in the following series of “Thermal Design Considerations” application notes. Thermal management should be considered up front at the product definition phase. Unfortunately, most often thermal design is an afterthought once the LED and LED-driver design is finished. A good thermal design must be an integral part of the overall system design along with the LED and driver design. The following series of thermal design related application notes are targeted for both beginner and advanced LED fixture designers and managers.