The 39th Annual Denver X-Ray Conference on Applications of X-Ray Analysis was held July 30 -August 3, 1990, at the Sheraton Steamboat Resort and Conference Center, Steamboat Springs, Colorado. The "Denver Conference" is recognized to be a major event in the x-ray analysis field, bringing together scientists and engineers from around the world to discuss the state of the art in x-ray applications as well as indications for future develop- ments. In recent years there has been a steady expansion of applications of x-ray analysis to characterize surfaces and thin films. To introduce the audience...