In the present study, measurements of electron temperature and density of a surface plasma generated during CO2 laser cutting of mild steel samples were carried out. A Langmuir probe was used to detect the electron and ion currents. For this purpose an electronic circuit was designed which reduced the noise effect during the tests. In order to compute the electron temperature and density, electron distribution was assumed to be Maxwellian and the plasma was assumed to be singly ionized. In addition, the data obtained from the present work were then related to data obtained from the previous tests. It is concluded that the electron number density obtained using an argon:oxygen gas mixture is lower than that obtained using oxygen alone. Cut quality improves at high electron temperatures and low electron densities.