Ureidopropyl　groups　were　used　to　functionalize　the　pore　channels　of　ethane-bridged　periodic　mesoporous　organosilica　by　the　co-condensation　of　1,2-Bis(triethoxysilyl)ethane　(BTESE)　and　ureidopropyltriethoxysilane　(UPTES)　in　the　presence　of　Poly(ethylene　glycol)-B-Poly(propylene　glycol)-B-Poly(ethylene　glycol)　(P123)　surfactants　under　acidic　conditions.　The　final　materials　were　investigated　in　detail　by　means　of　XRD,　TEM,　solid-state　NMR,　FT-IR　and　N-2　adsorption,　in　order　to　study　the　effect　of　ureidopropyl　groups　concentration　on　their　mesoscopic　order　and　pore　structure.　The　results　show　that　bridging　groups　in　the　framework　do　not　cleave　and　ureidopropyl　groups　are　attached　covalently　to　the　pore　wall　of　periodic　mesoporous　organosilica　after　functionalization.　The　mesoscopic　order　decreases　with　increasing　amount　of　UPTES　except　for　the　sample　with　20　mol%　UPTES　concentration,　which　exhibits　a　highly　ordered　two-dimensional　hexagonal　symmetry.　The　surface　area　and　pore　size　decrease　as　the　concentration　of　UPTES　increases,　but　the　materials　with　20　mol%　UPTES　still　preserve　a　desirable　pore　structure,　with　a　surface　area　of　565　m(2)/g,　a　pore　volume　of　1.1　cm(3)/g　and　a　mean　pore　size　of　10.1　nm.　(c)　2006　Published　by　Elsevier　Inc.