The barrier penetration model has been used to calculate the fusion cross sections of heavy ions and found to give a good description of the available experimental data. Based on this, we have calculated the reaction rates of CNO fusion at various temperatures and found approximate analytical expressions for their dependence on the temperature. For the 12C + 12C and 16O + 16O reactions, our results are significantly smaller than the results by Caughlan et al. [2]. Especially for 16O + 16O our rate is only a small fraction of theirs ( 1 7 − 1 20 ) depending on the temperature in the range T 9 = 0.5–5.0. The importance of this result for the evolution of massive stars, supernovae and nucleosynthesis is briefly indicated.