An accurate study of the potential energy surface of the ground state of the AlOH2 system has been performed together with a multi-configuration SCF and multi-reference CI analysis of the excited electronic states, in order to help understand the hydration experiments in which the Al atom has been found to react with water. Two critical transition states for the Al + H2O reaction appear to lie above the ground state reactants. On the other hand, the computed electronic spectrum of HAlOH and the behavior of the excited electronic states with some reaction coordinates are coherent with the experimental results. (C) 2009 Elsevier B. V. All rights reserved.