The selectivity of reactant rotational and vibrational energy upon reactive cross sections for the reaction OH + Cl-2 --> HOCl + Cl is investigated in detail by performing quasiclassical trajectory (QCT) calculations on a six-dimensional, analytically constructed potential energy surface (PES). The construction of the PES was based on ab initio molecular orbital calculations of the HOClCl system using the unrestricted second order Moller-Plesset perturbation theory approach. The quantum mechanical investigation produced three stationary points relevant to the title reaction, a transition-state configuration and two HOCl ... Cl-type complexes. Geometries, energies, and vibrational frequencies are reported for these structures. The analytical functional form for the PES has been developed following the Schatz-Elgersma formulation incorporating the Sorbie-Murrell potential energy term for the HOCl molecule. Extended three-dimensional QCT calculations at low and moderate collision energies covered several rotational and vibrational reactant states to produce a detailed study of the selectivity upon the reactivity of the system. The resulting dynamical features are the strong enhancement of reactivity when the vibrational content of the breaking band is raised and the exactly opposite effect when the vibrational excitation of the spectator OH bond is increased. The initial reactant rotation is shown to have a very minor influence on the dynamics.