(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..