We reformulated the expressions for the interpretation of surface plasmon resonance (SPR) signals presented in the paper of Jung and co-workers (Jung, L. S; Campbell, C. T.; Chinowsky, T. M.; Mar, M. N.; Yee, S. S. Langmuir 1998,14, 5636.) so that only two experimentally accessible parameters are needed to quantify the SPR signal of a coated sensor disk with unknown optical properties: a specific sensitivity and the specific decay length of the evanescent field. The sensitivity was measured using the refractive index difference between two different ionic strength solutions. The decay length was determined using the rate of adsorption of latex spheres while comparing these with theoretical predictions using the diffusion coefficients of these spheres. In addition, the errors involved in a linearized version of the equation were assessed.