Thermal decomposition of different polymeric materials was investigated by thermochromatography (ThGC), a temperature programmed pyrolysis chromatographic method. ThGC produces two-dimensional results; the co-ordinates of which are the retention time and the pyrolysis temperature at the time of sampling. Therefore, principal component analysis (PCA), on results from evolving factor analysis (EFA) successfully applied would decompose the complete data of each run into two parts: 'thermograms' and 'chromatograms'. Factor analysis at this stage compresses the data, making it more convenient for further analysis of the data structure composed of a few dozen of samples. The aim of this stage of the data analysis process is to extract 'real thermograms' as close as possible to the corresponding 'thermograms' - answering the question "which products are evolved at each temperature." Combination of 'chromatograms' and related 'thermograms' obtained on the first stage were used as characteristic vectors in the further analysis. Sets of significant 'thermograms'-'chromatograms' were subjected to PCA. Mapping of the polymeric samples onto planes defined by factors allows one to identify clusters as related to different classes of polymers, as well as different mechanisms of their thermal decomposition. The data was proven to give a very good basis for characterization of the samples by their polymer content.