The temperature dependence and the pressure dependence of the minimum ignition energies of n-butane-air mixtures were studied. The minimum ignition energies were measured by means of the capacitance spark ignition technique at room temperature, 323 K and 343 K, and at the atmospheric pressure and O. 168 MPa. The minimum ignition energies obtained at the room temperature and atmospheric pressure agreed with the reported values very well. At constant pressure, the minimum ignition energies of the mixtures having the same compositions decreased with increasing tentperature. At constant ternperatures, they decreased with increasing pressure and the degrees of their depressions increased as their values increased.