The Fifth International Congress on X-Ray Optics and Microanalysis was organized by the Institute of Applied Physics at Tubingen University in Western Germany from September 9th through 14th, 1968. Since 1956, when the First Conference was arranged in Cambridge, England by one of the pioneers in this field, V. E. CossLETT, the experts in the fields of X-Ray Optics and Microanalysis have met every third year to exchange their scientific experiences. Later meetings were held at Uppsala, Sweden in 1959, at Stanford, California in 1962, and at Orsay, Francein 1965. The participants in the 1968 Conference came from the following countries: Germany 140, France 60, Great Britain 55, USA 20, Netherlands 16, Switzerland 12, Austria 9, Sweden 7, Belgium 6, Japan 5, Italy 4, two each from Israel, Yugoslavia, Canada, Norway, Hungary and one each from Argentine, Poland, South Africa. As at the latest congress in Paris the following central topics were treated: General problems of X-ray optics, physical bases of electron beam microanalysis, quantitative problems of X-ray microanalysis, instrumentation, microdiffraction, applications to metal- lurgy, mineralogy, and biology.An exhibition showing some of the most modern instruments formed an important part of the conference. The Springer-Verlag, Heidelberg, deserves thanks for the careful and speedy work they have performed in printing these conference proceedings. We are further indebted to all contributors of this volume for their kind cooperation. Tubingen, August 1969 G. MoLLENSTEDT and K. H.