Abstract: Adsorption of molecules onto a thin metallic surface such as of gold, silver or copper is measured by surface plasmon resonance (SPR) using Fourier Transform (FT) spectroscopy. Reflectance spectra from a prism/metallic film sample surface at a fixed angle of incidence is measured with FT spectroscopy. The reflectance spectrum exhibits a pronounced minimum due to the SPR effect, which can be shifted by changing the angle of incidence or metallic film thickness. The position of the reflectance minimum shifts in wavelength with the adsorption of molecules onto the gold surface due to a change in the index of refraction at the interface. The FT-SPR sensor instrument provides wavelength stability and reproducibility of the resonance wavelength to permit detection of small wavelength shifts, and also substantially increases the spectral range over which the SPR measurements can be made.