In this paper, the integration of UWB and UHF technologies for RFID systems is investigated. A fast and energy efficient identification algorithm that makes use of UWB ranging is proposed for ISO/IEC 18000-6C tags. Compatibility with the standard, cooperation between the UHF and UWB technologies and solutions for asynchronism management are the main subjects of our analysis. Numerical results show that the proposed algorithm guarantees approximately 25% performance improvement in terms of success rate and energy consumption with respect to the ISO/IEC 18000-6C standard.