One of the first applications of lasers was for surgery on the retina of the eye. That, and the evident analogy to the old dreams of powerful heat rays, led many to predict that lasers would quickly be used for all kinds of cutting and welding, including surgical applications. It was soon apparent that laser sur gery could be performed in ways that caused little bleeding. Nevertheless, other surgical applications have been slower to arrive. One difficulty has been the enormous range of possibilities provided by the many different kinds of lasers. Infrared, visible, and ultraviolet light beams...