Evolution of chemical and textural-morphological features characterizing two native Argentinean hardwood species (Aspidosperma Quebracho Blanco Schlecht and Aspidosperma Australe) subjected to pyrolysis at different operating conditions is analysed by several techniques. Surface areas of raw materials and pyrolysed samples are evaluated from physical adsorption measurements employing N-2 at 77 K and CO2 at 298 K. The samples are also examined by optical and scanning electronic microscopy. Results point to significant feature changes,which are, in general, strongly affected by pyrolysis conditions, particularly temperature. Furthermore, kinetic measurements of woods pyrolysis are performed by non-isothermal thermogravimetric analysis, from ambient temperature up to 1123 K. A deactivation model reported in the literature, which predicts an increase of activation energy with reaction extent, successfully describes kinetic data for both species over the whole range of degradation temperatures.