Animal Health Economics is a relatively new subject, being developed to provide a quantitative insight into the economic effect of disease and disease control in livestock. Research in this field is focussed on both the further development of a more solid scientific framework of concepts and methods and its applications in quantitative model calculations. Three issues are especially of interest: (a) the losses of disease, (b) the profitability of preventive measures, and (c) the replacement decision of individual affected animals. All three issues concern complex problems, which have to be studied under imperfect veterinary knowledge and under a high degree of uncertainty. In this paper the basic economic framework and its applications in the underlying field are discussed and illustrated.