Effects of hydrostatic pressure up to 18000 kg/cm2 on the current-voltage characteristics of germanium Esaki diodes are reported. The pressure dependence of the peak currents IP, valley currents IV, peak voltages VP, valley voltages VV, and the exponential excess currents IX have been studied on sixteen germanium Esaki diodes. The results indicate that the semi-logarithmic plot of peak currents IP versus pressure P consists of two straight lines with different negative slopes. The intersecting point occurs in a pressure range from 5000 kg/cm2 to 9000 kg/cm2. The peak voltages VP change only slightly with pressure, while the valley voltages VV are independent of pressure within the limit of experimental errors. For most diodes the pressure dependence of the valley currents is the same as that of peak current. The onsets of the exponential excess currents move toward high voltages with pressure. The pressure dependences of the peak currents and exponential currents have been discussed. It is shown that the presence of two straight lines with different slopes may be related to different tunnelling processes. A pressure coefficiant of the energy gap Eg can be determined at a constant exponential excess current; the result is in good agreement with that given by other authors.