The　use　of　concrete-filled　hollow　structural　steel　(HSS)　columns　has　become　widespread　in　the　past　few　decades.　However,　these　members　are　subject　to　static　long-term　behaviors　under　sustained　loading,　a　common　phenomenon　in　concrete　structures.　Such　a　problem　has　not　been　addressed　satisfactorily　by　design　codes.　The　present　study　is　an　attempt　to　predict　the　time-dependent　behavior　of　concrete-filled　HSS　columns　by　means　of　a　model　that　is　proposed　by　ACI　209R-92.　Tests　on　the　behavior　of　concrete-filled　HSS　columns　with　square　sections　under　long-term　sustained　loading　are　performed,　in　addition　to　proposing　further　tests　on　the　static　ultimate　strength　of　the　composite　columns.　A　theoretical　model　of　analysis　to　account　for　shrinkage　and　creep　effects　on　concrete-filled　HSS　columns　under　sustained　loading　is　presented.　A　comparison　of　results　calculated　using　this　model　shows　good　agreement　with　test　results.　Finally,　formulas　for　the　calculation　of　the　ultimate　strength　of　the　concrete-filled　HSS　columns　subjected　to　long-term　sustained　loads　are　presented.