The information regarding the mechanistic details of selected systems of borane and borane anion reactions has been surveyed. For each family of reactions, the data from different investigations over a substantial time period were gathered together to make these data more accessible. The reaction systems studied were: preparation of B 3 H 8 - , the preparations, NMR spectra and structures of the five known B 5 anions, the preparation of bridge-substituted B 5 H 9 derivatives, the equilibrium between the isomers of Me-B 5 H 1 0 , conversions between nido and arachno structures in B 6 compounds and a variety of cluster growth reactions. Information and proposals regarding mechanisms are given where they are available. In some cases we have advanced proposals of our own. An important aim of this review is to stimulate additional experiments and calculations that will advance understanding of the mechanisms of reactions of boron compounds.