The changes in resistivity of silicon samples containing gold impurity, which are appropriately counterdoped with hydrogenic impurities, have been measured at hydrostatic pressures up to 30 000 kg cm-2 near room temperature. The changes are explained by a dependence on pressure of the ionization energy of the gold impurity. The pressure coefficient of the energy of a gold acceptor level near the center of the forbidden gap has been determined, relative to both band edges; the coefficient of the separation from the conduction band edge is twice that of the separation from the valence band. The sum of the two coefficients gives a pressure coefficient for the total energy gap of -1.5×10-6 eV kg-1 cm2 between 0 and 4000 kg cm-2 or -2.4×10-6 eV kg-1 cm2 near 20 000 kg cm-2. The low-pressure value is in agreement with previous, more direct, determinations. A donor level due to the gold, roughly 0.35 eV above the valence band edge, has a very low pressure coefficient relative to that edge. © 1962 The American Physical Society.