Since libraries first used RFID systems in the late 1990s, more and more libraries have identified the advantages of the technology. With advances in HF and UHF RFID, both alternatives are now viable in library applications. While some librarians are still skeptical towards UHF RFID as unproven in the library arena, the City University of Hong Kong implemented two pilot tests of the technologies. The Library formulated a set of criteria to evaluate UHF RFID against HF RFID as a possible library service transformation tool. This is to ensure that the selection of UHF or HF RFID is a rational one that is based on objective observation and analysis. The article provides background on the service transformation needs at the Library of the City University of Hong Kong. It reviews the use of HF RFID in the library arena and presents the latest development of UHF RFID. Results of the two pilot tests and how the University Library evaluated the two technologies are covered. (Contains 1 table.)