High energy pulsed and high power CW lasers are considered. The path of the photons is traced from generation in the laser cavity to interaction with a target. At each step along the path, the interaction between aerodynamics and laser radiation must be understood to avoid serious degradation of beam quality. Beam distortion effects are cumulative. Aero-optics as an interdisciplinary technical area has achieved a level of maturity where most pitfalls can be circumvented.