The explosion limits of air/C2H4/inert gas (N or CO2) mixts. were detd. at 1, 10, and 100 bar using an app. with elec. ignition and evaluation by the pressure threshold criterion, and simulations were performed using existing models. Whereas the lower explosion limit changed only little, a strong increase of the upper explosion limit was obsd. with increasing pressure. Empirical models describe the pressure dependence of the explosion limits of C2H4/air mixts. sufficiently exactly. The influence of the inert gas was simulated by a semi-empirical model.