Abstract
The derivation of a Boltzmann equation for homogeneous systems by Prigogine et al. has been generalized and simplified by an introduction of a binary collision expansion instead of the perturbation expansion of the resolvent operator for the Liouville operator. Such binary collision expansion makes the derivation much simpler than the perturbation expansion. The result, however, agrees with that of Prigogine et al. and the reason for the agreement is briefly discussed.