This project was undertaken to advance the experimental technology of x-ray absorption spectroscopy in the study of electrochemical interfaces. The objective was to establish the standard by which subsequent measurements would be evaluated. To this end we paid a great deal of attention to the details of the control of a large sample, the potential pitfalls related to artifacts in the data, and to high quality analyses of the results. These goals were met. Extended x-ray absorption fine structure (EXAFS) is capable of revealing the near neighbor environment of a specific element in a complicated system. By placing a monolayer of a foreign metal on an electrode, and studying this material, we hoped to reveal the geometry of the electrolyte in the first layer next to the sample. We chose Cu on Pt as the prototype, partly for its suitability regarding x-ray absorption edges, and also for its exemplary role as a strongly bound electrochemically controlled adsorption system. Our experimental design was based upon use of an unusually large sample (47 cm2) to obtain large signals. The sample was excited with grazing incidence x-rays, and the absorption structure associated with the Cu was monitored through the Cu Ka emission. We used a specially designed sample and electrolyte control system that enabled experiments to be performed with both p-and s-polarized incident radiation.