Results of ab initio calculations of the (H2O)(5)/(H2O)(5)(-) systems are presented. The main conclusions of the study are as follows: Based on the calculations we predict that water pentamer anions are metastable systems in agreement with their weak spectral manifestation in the gas-phase experiments of Bowen and co-workers; the excess electrons in all five structural isomers of the water pentamer anion found in the calculations are attached to the clusters by virtue of a dipole-electron interaction; the (H2O)(5)(-) anions found in the calculations are close in energy but have different vertical electron detachment energies ranging from 143 to 395 meV.