The collision integrals of various kinetic models are compared to those of the Boltzmann binary‐collision operator for gas mixtures. It is found that the Holway ellipsoidal model is unable to reproduce the Boltzmann result for the partial heat‐flow collision integral[&dgr;(12maca2ca)]abwhenma≫ mb. The Gross‐Krook and Sirovich models are found to be in serious disagreement with the Boltzmann operator with regard to the partial traceless‐pressure and heat‐flow collision integrals.