The grafting of polystyrene (PS) onto various polypropylene (PP) containing substrates, previously treated by exposure to a plasma, has been followed by Raman microspectroscopic mapping. The substrates consisted of either pure PP, or blends of PP and ethylene-propylene rubber (EPR). For exactly the same section of polymer surface, Raman spectra were obtained at 1 micrometers intervals for small sections of each substrate, the surface after plasma-treatment, and the surface after PS grafting. Typically, the size of the sections studied was 50 micrometers X 50 micrometers . Raman maps were constructed indicating the crystallinity variation across the surface, and also the distribution of the EPR component in the substrate, and after plasma treatment. Raman maps were also constructed to show the distribution of the PS at the surface after the grafting reaction. Grafting was found to be heterogeneous. The overall amount of grafted PS depended on the amount of EPR in the substrate. For a particular substrate, increased concentrations of grafted PS were correlated with positions on the surface which had higher EPR after plasma treatment.