Reliable electronics packaging is important in high pressure and high temperature instrumentation applications. Oil well instrumentation systems, process monitoring systems and distributed engine control systems are typical examples of applications in which direct pressurizing the electronic system will reduce the package size. Integrated circuits that function reliably at 200 °C are becoming commercially available, and we have previously shown that these components can be reliable at pressures up to 1000 bar. Thus our interest is focused towards failures related to the passive components, the material choices made and the packaging processes used. In the current work passive components and interconnection system submerged in silicone oil were stressed by pressure cycling in the range of 1 - 1000 bars at temperatures from 20 – 200 °C. A total of 150 pressure cycles have been achieved. In these stress tests the performance of via holes in thick film alumina substrate, different type of wire bond metallization systems, thick film resistors, thin film chip resistors and ceramic chip capacitors were evaluated. There is no clear indication that the pressure cycling to any extent do speed up the failure mechanism for neither the passive components nor the interconnection systems. Ceramic chip capacitors do not show any erroneous behavior when subject to pressure cycling as they do when subjected to long term static pressure. Thin film resistors have a pressure dependent sensitivity less than 200 ppm in the range from 1 - 1000 bars. This is one decade lower than the corresponding thick film dependent sensitivity.