This book contains selected papers from a workshop on modern statistical methods in toxicology held during the EUROTOX '90 conference in Leipzig. The papers deal with the biostatistical evaluation of the commonly used toxicological assays, i.e. mutagenicity, long-term carcinogenicity, embryotoxicity and chronic toxicity assays. The biological background is considered in detail, and most of the related statistical approaches described. In five overview papers, the present state of the art of the related topics is given, while in several contributed papers new approaches are discussed. The most important features are: - A new view on the per-litter analysis problem in em- bryotoxicity assays. - A highly sophisticated treatment of the so-called muta-tox problem in mutagenicity assays. - A detailed discussion of the multiplicity problem based on the closed testing procedure. This volume provides readers with an overview of modern biostatistical methods for several toxicological assays and is in part intended for direct, practical use.