Micro-thermal analysis employs an active heated tip in a scanning probe microscope. This allows topographic and thermal imaging of surfaces to be carried out and permits localised thermal analysis of selected areas of material. In order to provide a means for spatially resolved chemical characterization, a method of trapping the gases that are evolved when the thermal probe is used to pyrolyze the surface has been developed. The trapped gases can then be thermally desorbed and passed into a GC-MS system for separation and identification. With this system it is possible to ablate a small (< 10 m x 10 mum) area of a sample (or a domain, feature or contaminant) and elucidate its composition. This paper presents initial results for a homogeneous polymer (poly(methyl methacrylate))- and a heterogeneous polymer blend (polystyrene/poly(alpha -methyl styrene)).