Events increasingly play a major role as important attractions in tourism. Like with other attractions, commonly comprising permanent built infrastructure, changing patterns of size and catchment areas are evident. Most strikingly those changes are identifiable, concerning financial inputs. Frequently, events are important means for city and regional marketing activities. Especially in cases, where public funds are used, evidence is to be provided on whether the money was well spent. The paper shows, which impacts events might have and how they can be measured. The BUGA 2005 in Munich is used to implement and discuss the methods. Concerning this case study a net impact effect for the tourism sector is calculated.