Descripción: A new polymeric phase of zinc(II) oxydiacetate, catena-poly[[[diaquazinc(II)]-μ-oxydiacetato] hydrate], {[Zn(C4H4-O5)(H2O)2] ·H2O}n, isomorphous with the Co homologue [Hatfield, Helms, Rohrs, Singh, Wasson & Weller (1987). Proc. Indian Acad. Sci. Chem. Sci. 98, 23-31], is reported. It presents a chain-like structure, generated by ZnO6 cores which are bridged by carboxylate groups in an anti-anti conformation along the unique crystallographic b axis. The chains are held together through hydrogen-bonding interactions with the three water molecules.