The result of an unsteady analysis of the conditions leading to a wedge-triggered detonation wave in a premixed hydrogen-air supersonic flow is presented. The configuration of interest here corresponds to a delayed oblique detonation wave (ODW), resulting from an oblique shock wave (OSW) transition. Different types of steady and unsteady configurations are evidenced numerically. The computed conditions for the self-ignition and stationary solutions that are obtained are discussed from the point of view of kinematic and quasi-steady arguments. The results of the calculations are examined in the light of the available experimental data. (C) 2000 by The Combustion Institute.