mTo provide a potential energy surface (PES) for a three-dimensional vibrational model of the dissociation dynamics of ammonia in the A state, accurate MRD-CI computations were carried out for a wide range of displacements in the out-of-plane and in-plane bending coordinates along the H-NH2 dissociation coordinate. Some characteristic features of the A-state PES, such as the height and position of the barrier to dissociation and the dependence of the PES on the out-of-plane angle, differ noticeably from earlier work on this system. The values for the height of the barrier computed from the MRD-CI extrapolation, full CI, and secular equation estimates are 0.38, 0.34, and 0.32 ev, respectively. 0