Positive and negative corona characteristics of air and nitrogen are determined experimentally for coaxial cylindrical electrode geometry with gas temperatures from 300°K to 1100°K and with pressures from 0.1 to 8 atmospheres. Over this range, positive corona characteristics appear to be functions of gas density only. On the other hand, negative corona characteristics depend on gas temperature as well as gas density. At high temperatures both positive and negative coronas show instabilities which are pressure dependent.