Summary: This paper discusses the evaluation of university libraries from two standpoints, namely, total measure and ratio measure, and the 24 university libraries in Taiwan are adopted for empirical study. The total measure is based on the services and total resources, including collections, personnel, expenditures, and buildings that a university library is providing for its patrons. The total amount of these five factors weighted by their importance is calculated for each library for comparison. It is a measure of the size of a library in an aggregated sense. The ratio measure, which takes into account the clients sharing the resources and services, measures the extent that a library satisfies the standards. In both cases, the data envelopment analysis methodology is utilized. To prevent the ignorance of some factors in calculating the index for comparison, the assurance region concept is applied. Good libraries should have high indices in both measures. The empirical results show that only the libraries of National Taiwan University, National Cheng Kung University, National Cheng Chi University, and National Chung Cheng University provide sufficient resources and services for their clients.