To my mind, the superoxide radical discovered by Linus Pauling more than 50 years ago is about to become a major issue in Ameri can medicine. Uncannily, Pauling's early focus on vitamin C has pointed the way to the whole catalogue of free-radical scavengers, which we in medicine will be using in the coming decade. In ophthalmology, the basic scientists have been talking about the role of free-radical induction by light for some time. They have accumulated an increasing amount of evidence supporting the idea that prolonged light exposure contributes to cataract development and retinal degeneration. Through Clinical Light Damage to the Eye, we hope to bring this message to the practicing ophthalmolo gist. Because Dr. Pauling's work bears so strongly on the key issue of free-radical damage, and because of my own great respect for him as a scientist and a man of rare courage, I invited Dr. Pauling to write the foreword to Clinical Light Damage to the Eye, which follows.