Radio Frequency Identification (RFID) devices and related technologies have received a great deal of attention for their ability to perform noncontact object identification. Systems incorporating RFID have been evaluated from a variety of perspectives. The authors constructed a networked RFID system to support event management at NetWorld+Interop 2004 Tokyo, an event that received 150,000 visitors. The system used multiple RFID readers installed at the venue and RFID tags carried by each visitor to provide a platform for running various management and visitor support applications. This paper presents the results of this field trial of RFID readability rates. It further addresses the applicability of RFID systems to visitor management, a problematic aspect of large-scale events.