Summary NMR analyses of spin coupling constants, nuclear Overhauser effects and Gd(III)-induced relaxation rates were made of ribosyl adenosine 5′,5″-bis(phosphate), [Ado(P)-Rib-p], in aqueous solution. The α-configuration of the Cl″ atom of the Rib-P moiety was confirmed. The Ado(P) moiety takes the anti form about the glycosidic bond, the gg form about the exocyclic bond, and the 2′-endo and 3′-endo forms of the ribose ring with nearly equal fractional populations. The ribose ring of the Rib-P moiety preferentially takes the gt/tg-2″-endo form. The Ado(P)-Rib-P molecule has a fairly extended overall molecular conformation.