Part A. Ecotoxicological Models: General Considerations. 1. Introduction. Needs of models in ecotoxicology. 2. Modelling Concepts. Modelling and ecotoxicology. Definitions of modelling elements. The modelling procedure. Types of models. Characteristic features of ecotoxicological models. 3. Use of Ecotoxicological Models in Management. Complexity of ecotoxicological models. Characteristic features of ecotoxicological models. An overview: The application of models in ecotoxicology. 4. Estimation of Physical-Chemical Parameters in Ecotoxicology. Use of benchmark chemicals. Estimation of critical temperature and boiling point. Estimation of Henry's constant and the vapour pressure. Estimation of solubility and partition coefficient. Estimation of adsorption isotherms. Estimation of air/soil exchange coefficients. Estimation of the air/water exchange coefficient. Estimation of evaporation rate. Estimation of the hydrolysis rate coefficient. Estimation of photochemical reaction rate coefficients. Summary. 5. Estimation of Biological Parameters in Ecotoxicology. Estimation of bioconcentration and bioaccumulation. Estimation of the biodegradation rate. Estimation of toxicity. Summary. 6. Types of Models of Particular Interest in Ecotoxicology. Application of models in ecotoxicology. Models with risk assessment component. Fugacity models. Part B. Case Studies of Ecotoxicological Models. 7. Modelling the Distribution of Chromium in a Danish Firth. Case study description. Model description. Application of the model for environmental management. 8. Contamination of Agricultural Products by Cadmium and Lead. Introduction. Sources of cadmium and lead contamination in agriculture. The model. Model results. Discussion and conclusions. 9. Modelling the Release of Copper from Lake-Sediment.