The barrier associated with the dissociation and recombination of ozone has been calculated using highly correlated ab initio methods, Our calculations show that. for fixed equilibrium values of the bending angle and one bond distance. there is a very small barrier. 100 cm(-1). as opposed to much larger values previously reported. When the saddle point geometry is optimized, the reaction path still contains a barrier but the top of the barrier lies below the dissociation limit. (C) 2002 Elsevier Science B.V. All rights reserved.