In this paper a methodology to develop simulation models is presented. The methodology is based on amulti-level simulation model which allows flexibility and process analysis. The present work starts fromapplied researches in different SME enterprises. Enterprise management often needs easy and fastdeveloped tools to increase production capacity and flexibility. In many cases performances increase ispossible only adopting a BPR (business processes reengineering) approach. Nevertheless the resistanceto a BPR approach is underlined in recent bibliography. The proposed approach consists of a three stagesmethodology, named VirtES (Virtual Enterprise Simulator). VirtES methodology was first applied toceramic tiles enterprises. The results achieved encourage the adoption to other industrial field.