This volume contains the texts of the Invited Lectures pre sented at the NATO Advanced Study Institute PHOTOPHYSICS AND PHOTOCHEMISTRY IN THE VACUUM ULTRAVIOLET, which was held at the Interlaken Lodge in Lake Geneva, Wisconsin USA, August 15-28, 1982. This ASI was the third in a series of NATO Institutes de voted to a study of the physical and chemical transformations undergone by atoms and molecules after absorption of high-energy (VUV