A radio frequency identification (RFID) monitoring system (12) for monitoring a plurality of RFID tags, and in particular for monitoring a plurality of vials incorporating such tags and stored at a low temperature, (eg.−80° C.) within a storage unit (10), for example a freezer. The RFID system (12) comprises an RFID reader (28) and at least one antenna (34a-34i) for transmitting and receiving RF signals to communicate with the RFID tags. The system (12) further includes an electronic switch (38), preferably a FET switch, interposed between the RFID reader and the at least one antenna (34a-34i) to connect a particular antenna (34a-34i) to the RFID reader (28) and transmit RF signals from the antenna (34a-34i) to the RFID tags. The switch (38) is controlled to intermittently connect the antenna (34a-34i) to the RFID reader (28) to regulate the power of the RF signal transmitted from the antenna (34a-34i). The system enables an RFID tag to operate at low temperatures. Preferably the switch (38) and antenna (34a-34i) are integrated together, and in particular integrated into a shelf (22) of the storage unit (10).