Dynamical pathways for the interconversion between two stable (H2O)(9) derived from the D-2d octamer have been investigated using the transition path sampling formalism. Instantaneous normal mode analysis reveals that the dynamics over the ensemble of transition states is characterized by the concerted translation of three molecules. At a total energy E = -76 kcal/mol. the characteristic time for the interconversion is of the order of 0.5 ms. This estimate compares well with predictions from classical RRKM theory. (C) 2002 Elsevier Science B.V. All rights reserved.