In　this　paper,　we　report　on　an　underground　water-source　water-loop　heat-pump　(UWSWLHP)　air-conditioning　system　for　a　tall　apartment　building　in　Beijing.　Water　at　14　degrees　C　was　used　as　an　external　low-temperature　heat-source.　By　analyzing　field-test　data　for　two　years,　the　authors　assessed　the　operating　and　controlling　conditions　of　the　system.　Based　on　the　electricity　consumed　by　public-use　air-conditioning　power　equipment　and　terminal　heat-pumps,　the　authors　put　forward　an　overall　evaluation　of　the　energy-conservation　characteristics　of　the　system.　(c)　2005　Elsevier　Ltd.　All　rights　reserved.