This paper describes the theoretical design and practical implementation of a set of performance indicators in a public library system in London (England). Bromley Libraries has 15 branch libraries and serves 300,000 people. The need for improved management control by assessing performance and monitoring progress, library restructuring, and government initiatives all prompted the development of a set of performance indicators. This paper analyzes the aims and objectives of the project; how the indicators were selected; production criteria and the chosen set of indicators; what was learned from the project; and how the indicators are used in practice. Implementation challenges included: obtaining staff commitment which is crucial for the valid and continued use of the indicators; defining consistent terms; and ensuring validity, reliability, and credibility. The main advantages of the performance indicators are as a practical management tool for comparing branches over time, systematic stock provision, and more informed decisions; as a means of preempting problems; and as a platform for further informed questions. In public libraries, both what is measured and how the results are interpreted should reflect the aims and objectives of the particular service. The main test of a good set of indicators is their ability to determine whether a service is effectively fulfilling its chosen objectives. Figures show sample performance data. (SWC)