The importance of recovering waste materials generated by industrialised societies is mainly due to the environmental impact they have, and one of the principal problem areas is tires. In recent years, an enormous amount of tires have been recycled. Metals contained in them have been recovered and the tire particles have been used in diverse applications. A third material that appears in the recovery process is the fibers, which act as reinforcement. Before addressing the possible reuse of these fibers, it is necessary to characterise and identify them. The diverse techniques of thermal analysis allow these fibers to be identified through melt point analysis, the results of which show the presence of polyamide 6 and 6.6. Moreover, the combination of pyrolysis-gas chromatography/mass spectrometry corroborates the identification made with the techniques previously mentioned and also indicates the presence of certain additives used in the manufacture of tires, such as resorcinol and benzothiazole. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113:2136-2142, 2009