An RFID tag monitoring system with multiple reader units each equipped with processing capacity sufficient to enable the unit to operate autonomously under its own command and control as well as to register in its individual memory the identity of all of the items that potentially could be present at any particular time at a zone or zones to which it is assigned as well as the particular zone at which a specific RFID tagged item is found; data compression at the reader units permits timely reporting of inventory to a main computer.