We have presented a molecular dynamics study of the dynamics of breaking and structural relaxation of hydrogen bonds at vapour-water and metal-water interfaces. For both interfaces, the relaxation of hydrogen bonds is found to occur at a slower rate than that in bulk water. However, the dynamics of inter-region hydrogen bonds, where one molecule of the bonded pair belongs to interface and the other to its adjacent layer, are found to be faster than even the bulk hydrogen bonds. The results are explained in terms of the energies of hydrogen bonds and the frictions that act on the rotational and translational motion of water molecules at interfaces. (C) 2004 Elsevier B.V. All rights reserved.