Lasers have historically been considered in the context of weapons, but recent progress has also permitted us to consider using lasers for more subtle applications such as designation, tracking, and discrimination. In this paper, we will review the state of the art of active tracking, including effects such as laser beam quality, diffraction, atmospheric turbulence, and other aspects of laser interactions with the propagation environment. We will present the theory for using lasers in relatively low-power tracking applications.