This　paper　introduceds　a　portable　refrigeration　system　based　on　development　of　micro　electro-mechanical　systems　(MEMS)　technologies,　and　describes　how　the　entropy　generation　changes　at　each　component　in　a　vapor　compression　refrigeration　system　as　the　system　scale　is　decreased.　Although　the　quantitative　evaluation　of　the　entropy　generation　is　not　made　here,　it　is　clear　that　the　micro　compressor　is　the　most　difficult　component　to　be　miniaturized　in　a　portable　refrigeration　system.　If　a　portable　vapor　compression　refrigeration　system　is　expected　to　be　successfully　operated,　a　great　deal　of　efforts　must　be　made　to　develop　a　workable　micro　compressor　and　to　minimize　the　refrigerating　output　loss　of　the　evaporator.