An island refrigerated display case can be constructed so as to in effect constitute to back-to-back display cases that can be arranged as a separate aisle within a supermarket. Such an island refrigerated display case has two interior display spaces separated by a partition wall with each display space having its own access opening so as to enable refrigerated products to be removed from that portion of the case. Encircling each of the interior display spaces is an associated refrigeration air conduit. Each of the refrigeration air conduits has an inlet and outlet opening positioned so as to direct air across the corresponding access opening for the interior display space. Thus during the refrigeration cycle of operation, a refrigerated air curtain is formed between the corresponding outer wall and the center partition wall so as to extend across the associated access opening. The portions of the refrigeration air conduits that extend through the partition wall can be joined so as to form a single chamber. In this manner, the evaporator coils can be located either along each of the refrigeration air conduits or in the central chamber within the partition wall. The island display cases are defrosted by an ambient air defrost system in which ambient air is drawn into and circulated through the refrigeration air conduits for defrosting any frost buildup within such conduits.