(S)-5-Benzylimidazolidine-2,4-dione monohydrate.

The crystal structure of the title compound, C(10)H(10)N(2)O(2).H(2)O, also known as L-5-benzylhydantoin monohydrate, is described in terms of two-dimensional supramolecular arrays built up from infinite chains assembled via N-H...O and O-H...O hydrogen bonds among the organic molecules and solvent water molecules, with graph-set R(3)(3)(10)C(5)C(2)(2)(6). The hydrogen-bond network is reinforced by stacking of the layers through C-H...pi interactions.