The stochastic approach to chemical kinetics discussed previously is specialized to dilute gas reactions. In this limit the stochastic master equations are Boltzmann equations for which collision theory is used. Internal rearrangement reactions, both in the presence and absence of inert diluent, and bimolecular reactions, in the absence of inert diluent, are discussed in some detail. In the latter case the "reservoir" role must be played by translational and internal degrees of freedom of the reactants (and products) themselves. The rate constants for the reaction can be explicitly calculated in terms of cross sections in both the limit of long-lived (i.e., internally equilibrated) and that of short-lived (decomposing before exchanging energy with other molecules) "activated complexes." It is found that the Arrhenius temperature factors are identical in these two limits. In addition the "frequency" factors are similar but involve slightly different averages (over energy) of the same cross sections.