The electron-ion recombination coefficient γ and the avalanche coefficient δ = (α − a) · vd, where α and a are the ionizat ion and attachment coefficients respectively and vd the drift velocity of the electrons, have been experimentally determined in a self-sustained CO2-laser system (1:1:3 mixture) as a function of the E/N value. For low voltages we found the expected decrease of the recombination coefficient for increasing E/N values. However, it appears that for larger voltage the recombination coefficient increases sharply for increasing E/N values. The measurements of δ show a much smaller value than expected from theoretical calculations. This must be explained by a lower value of the electron-energy distribution function for higher energies, which may be consistent with our measured high recombination probability for electrons having high energy.