The book is for those interested in modeling exposure to chemicals. It contains two parts one is the text book which allows the reader to learn about the dynamic behavior of chemicals in our environment. Basics of exposure estimation, mathematics and chemistry are explained in the first chapters, followed by a guide to exposure models for all environmental media. Part two is the software tool "CemoS" (Chemical exposure model System) which includes nine exposure models, a substance database with twelve data sets, data estimation routines, quality assurance tools and a hypertest online help. The disk is quickly installed and runs on DOS 3.3 or higher (up to WINDOWS NT). The comprehensive CemoS manual is also included. It is identical to the online help. All equations used in the program are described in detail, making the calculations fully transparent. Exercises with solutions, example calculations and a data base help the reader to learn about and apply exposure models.