There is increasing interest in arranging festivals or special events in many cities. This paper presents an econometric model to account for the tourism accommodation impact of such events. The autoregressive count data model incorporates some of the more important factors in the planning and evaluation of an event, such as spare capacity, displacement effects and the costs that visitors face. The results for two large Swedish festivals indicate that there are some displacement effects but that the net tourism effect is positive, since the average visitor stays longer during festival periods. In the final year of the sample the festival increased the accommodation receipts for the hotels in Stockholm and Gothenburg by 2% and 6%, respectively.