We report a rational synthetic approach for the preparation of the negatively charged water tetramer anion, the only member of the homogeneous (H2O)(n)(-) series that has been curiously 'missing' in previous reports of these cluster anions. The synthesis was carried out using argon cluster-mediated anion formation. The identity of the (H2O)(4)(-) cluster is confirmed using negative ion photoelectron spectroscopy, and the resulting spectrum suggests the presence of three isomeric forms for this species. (C) 2004 Elsevier B.V. All rights reserved.