Accurate optical modeling of illumination systems requires, among other things, an accurate characterization of the light sources used in the system. The problem is that there is no single acceptable definition of 'accurate' that applies to all circumstances. What is determined to be acceptably accurate must also be tempered with analytical efficiency, meaning that the ideal light source model must contain just enough accuracy to produce acceptable results in the quickest manner possible. Finally, the modeling technique must also be practical to implement given that the technique needs to be applied to the large number of light sources in use today. There are many light source modeling techniques already used in practice and it is worth considering the appropriateness of the various techniques for the applications to which they are being applied. This paper starts with a description of the different aspects of light source models and their modeling techniques. The importance of the different aspects is then summarized for a range of applications. The goal of the paper is to present a set of guidelines that can be referenced by designers interested in selecting the most appropriate type of light source model for their range of applications.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.