While it is widely acknowledged that the performance improvement in current biometricsbased personal authentication systems is necessary, it is not clear what mechanisms could be used to improve the performance. In this paper, we formulate the problem of multiple biometrics integration and examine whether the improvement in performance could be achieved from integrating multiple biometrics. For two practical and commonly used situations of multi-biometric integration, we analyze the performance gains. We also demonstrate empirically that integration of multiple biometrics does indeed result in a consistent and significant performance improvement.