During the last decade, in studies of bimolecular reaction dynamics by both experimentalists and theoreticians, there has been increasing emphasis on reactions beyond the three-atom case, traditionally represented by A + BC --> AB + C. As part of this progress, four-atom reactions of the type AB + CD --> ABC + D have attracted much attention. Within this class of reactions, for both theoretical and experimental reasons, the system: OH + H-2 reversible arrow H2O + H has emerged as a prototype. In reactions involving four atoms, this reaction now occupies the place held by the H + H-2 --> H-2 + H and F + H-2 reversible arrow HF + H reactions amongst three-atom reactions. In this article, we review the experimental data for the kinetics and reaction dynamics that are available for the forward and reverse reactions, OH + H-2 reversible arrow H2O + H and compare these results with the current state of theory for this prototypical system. We also suggest future experimental and theoretical studies that are needed to bring our understanding of this reactive system to the level of that for the H-3 and FH2 systems.