Indications for light-based treatments, such as lasers, UV phototherapy, and photodynamic therapy, are rapidly increasing within the arena of skin disorders. Physicians can remain current in their understanding of these modalities if they understand a few basic principles outlined in this article. Once these concepts are understood, all the rapid advances can be kept in perspective and physicians can apply the most appropriate technology to the care of their patients while informing them about the limitations of overmarketed but poorly proved strategies.