Mainz was selected the "City of Science" for 2011 by the Donors' Association for the Promotion of Sciences and Humanities in Germany [Stifterverband für die Deutsche Wissenschaft]. The JGU Center for Quality Assurance and Development evaluates and supervises the entire project. In particular, the project focuses on the aspects of effects and sustainability. The evaluation consists of three phases. While in the first phase, the goals, expectations, and initial approaches of network building are determined, the emphasis in the second phase is on the visitors’ assessment of individual initiatives and major events like the Summer of Science and the Spektrale exhibition. In the third phase, the focus of attention will be on the long-term effects of the distinction in terms of science-based urban development beyond 2011. Thus, issues like sustainability and further development of projects and event formats, the institutionalization of networks and communication among the various stakeholders from the city, industry, science, education, the cultural world, and the public will be examined. Finally, the sustainable effects of having been a “City of Science” for the further development of the city of Mainz are to be discussed.