We have derived the effect of steady heat flux on the rate of chemical reaction based on the line-of-centers model using the explicit velocity distribution function of the steady-state Boltzmann equation for hard-sphere molecules to second order. It is found that the second-order velocity distribution function plays an essential role for the calculation of it. We have also compared our result with those from the steady-state Bhatnagar-Gross-Krook (BGK) equation and information theory, and found no qualitative differences among them. (C) 2003 Elsevier Science B.V. All rights reserved.