The complete active space valence bond (CASVB) method is an approach for interpreting complete active space self-consistent field (CASSCF) wave functions by means of valence bond resonance structures built on atom-like localized orbitals. The transformation from CASSCF to CASVB wave functions does not change the variational space, and thus it is done without loss of information on the total energy and wave function. In the present article, some applications of the CASVB method to chemical reactions are reviewed following a brief introduction to this method: unimolecular dissociation reaction of formaldehyde, H2CO → H2 + CO, and hydrogen exchange reactions, H2+X→H+HX (X = F, Cl, Br, and I).