When determining interventions against threatening infectious diseases such as HIV-infection, severe acute respiratory syndrome (SARS), smallpox and pandemic influenza, the use of mathematical models of the spread of infectious diseases is becoming increasingly popular. These models contribute to the structuring of the knowledge already available in various disciplines, to finding epidemiological connnections, to demonstrating lacunas within the pool of knowledge and to the comparison of the expected effects and costs of preventative and intervention measures. The use of models leads to a 'made-to-measure' analysis ofthe effects and costs of preventative and intervention measures which takes account of the specific characteristics of infectious diseases. The integration of knowledge from various disciplines can be supported by more research into the theoretical epidemiology of infectious disease and by better integration of mathematical models into policy development. The resulting and better foundations of this policy that are achieved by means of infectious disease modelling translate into more effective combating of infectious disease.