This volume consists of the revised versions of most of the main papers given at the first Seminaire Europeen de Statistique on Chaos and Neural Networks and at the subsequent Study Institute on other types ofnetworks, held at Sandbjerg/Aarhus University from 25 April to 7 May 1992. The aim of the Seminaire Europeen de Statistique and the Study Institute, in which about 35 young statisticians from all over Europe participated, was to provide talented young researchers in statistics with an opportunity to get quickly to the forefront of knowledge and research in the statistical aspects of chaos and networks. Accordingly the papers in this volume all have a tutorial character and it is hoped that they will be found broadly useful. The first Seminaire Europeen de Statistique was organized by O.E. Barndorff-Nielsen, Aarbus University; D.R. Cox, Nuffield College, Oxford; Jens Ledet Jensen, Aarbus University; Wilfrid S. Kendall, University of Warwick; and Gerard Letac, Universite Paul Sabatier, Toulouse. It is hoped in the future to arrange further Seminaires Europeens de Statistique, each one devoted to one or two research topics of great current interest and activity. The Seminaire Europeen de Statistique and Study Institute was supported by the Directorate General for Science and Development of the European Communities and by the Danish Research Acad emy, and their support is gratefully acknowledged.