The evaluation activity of the Library System of the University of Florence is recently resulted into a customer satisfaction survey. The book collects this experience and illustrates the premises, the stages of implementation, the statistical and library science methodologies. The survey is the culmination of a path inaugurated with the reorganisation of the Library System in 1994. Since that year, monitoring has been established as an essential part of the management process. After a few years dedicated to improving quality, users were invited to comment on the services, in relation to actual use and the degree of satisfaction.