This contribution summarizes the design and implementation of a novel experimental tool for the investigation of thin polymer films and interfacial architectures: a classical surface plasmon spectrometer is combined with a high pressure cell, thus allowing for the optical characterization of polymer layers at pressures up to 200MPa and over a temperature range of 10°to 120°C. We demonstrate the excellent performance of this combination setup by presenting a few typical results obtained with this instrument. These include, first, the determination of the pressure- and temperature-dependent refractive indices of the pressurizing media used in these studies, i.e., water, methanol, ethanol, and supercritical CO 2 (scCO 2 ), the pressure dependence of the glass transition temperature in thin poly(ethylmethacrylate)films, and the pressure-dependent collapse behavior of surface-grafted poly(N-isopropylacrylamide)gels in water. The final example then concerns a further extension of the setup by an electrochemical cell offering investigation of processes like heterogeneous electron transfer reactions at high pressure. We demonstrate by a few results obtained with the electropolymerization of bithiophene that the pressure is not only a thermodynamic variable that determines–just like the temperature–the physical properties of thin films, but it also constitutes an important process parameter during the preparation of polymer coatings.