A new in situ method of analyzing changes occurring to polymeric surfaces has been generated by the combination of atomic force microscopy (AFM) and surface plasmon resonance (SPR) in a novel instrument which can simultaneously acquire data from these two techniques. The application of this;instrument provides new insights into the dynamic changes occurring to a thin biodegradable polymer film when the surface of this film is exposed to a hydrolyzing environment. The AFM data enable the visualization of the topographical changes that result from degradation, whilst the SPR monitors the kinetics of the removal of polymer material from the film surface. The degradation of a spun cast thin film of a poly(ortho ester) is analyzed in this study. The,combined AFM/SPR data record the erosion of the thin film on the SPR sensor as degradation progresses. The pH sensitivity of the hydrolysis of the poly(ortho ester) film is explored by dynamically altering the pH during degradation to highlight the sensitivity of the instrument in the quantification of the degradation process.