An analysis of the ignition of H-2- and CH4- containing mixtures at high temperatures under the action of a nanosecond high-voltage discharge has been performed both numerically and experimentally for a wide range of parameters. A comparison of the equilibrium and nonequilibrium excitation was performed. The preliminary numerical analysis of ignition efficiency helped to plan experimental investigations of the initiation of the ignition by nanosecond discharge at high temperatures. A novel experimental scheme for the investigation of ignition delay at high temperatures under the action of a high-voltage nanosecond discharge has been developed. Electrical parameters on a nanosecond time scale and the ignition processes on a microsecond time scale were investigated. Ignition delays for different mixtures, gas pressures and temperatures were obtained experimentally. The dependence of the ignition delay upon temperature, high voltage amplitude, and the energy release into the discharge was determined experimentally for H-2-O-2, H-2-air and CH4-air mixtures diluted with argon or helium. Obtained data were compared with the results of numerical calculations. (C) 2003 The Combustion Institute. All rights reserved.