Kinetics of thermal decomposition of zinc and cadmium hydroxides along with their halide (Cl, F) derivatives are reported. The kinetic results are discussed in terms of the appropriate reaction mechanism. The rates are also discussed using activated complex theory in a manner outlined by Cordes (9) where the effect of molecular rotation in both the reactants and the activated complex is considered. Furthermore, the abnormally high preexponential factors are speculated to have their origin in an active translational mode on the surface.