The 38th Annual Denver Conference on Applications of X-Ray Analysis was held July 31 - August 4, 1989, at the Sheraton Denver Technical Center, Denver, Colorado. The conference alternates emphasis between x-ray diffraction and x-ray fluorescence, and this being an odd year the emphasis was on diffraction. Thus the Plenary Session was slanted toward diffraction in general and thin film analysis in particular. The Plenary Session on x-ray analysis of thin films did not just happen this year but really began four years ago with Paul Predecki suggesting a special session devoted to thin film techniques. The session generated a great deal of interest, so Paul suggested that a workshop on thin films should be slated for the 1987 conference. A full day was devoted to the workshop, which was split into a half day on epitaxial thin films and the other half day on polycrystalline thin films. The workshop attendance indicated a great deal of interest in this topic, leading to this year's Plenary Session. The first two speakers of the Plenary Session (B. Tanner and K. Bowen) have been key throughout the thin film activities. They were invited speakers for the 1985 special session on thin films and instructors for the 1987 workshop on epitaxial thin films.