A novel high-pressure set-up is presented that allows for the simultaneous characterization of interfacial reactions and thin films by surface plasmon optical techniques, as well as by electrochemical methods. The current configuration uses a grating coupler for the resonant excitation of surface plasmons at the (gold) metal \ dielectric interface with the metallic substrate serving at the same time as the working electrode in a three electrode electrochemical configuration. Using the same electrolyte as the pressure medium experiments up to about 50 MPa are reported. Firstly, some performance characteristics of the cell we discussed on the basis of CV measurements with hexacyanoferrate as a quasi-reversible redox system. Then the electropolymerization of bithiophene in acetonitrile solution at different cell pressures is presented. (C) 2003 Published by Elsevier Science B.V.