Aim: to evaluate ex-vivo the sealing ability of Thermafill system plus conventional sealer. Methodology: Thirty-two root-canals of single- and multi-rooted teeth with indication of extraction or amputation, were instrumented in vivo using the ProTaper (Dentsply-Maillefer, Ballaigues, Switzerland) instruments, NaOCl 1% and EDTA 17%. Working-length was set using Morita TrZX(Morita Mfg.Corp.-Japan) 0,5 mm short to apex. Root canals were obturated using the Thermafill system(Dentsply-Maillefer, Ballaigues-Switzerland) with sealer AHPlus(Dentsply-DeTrey GmbH, Konstanz-Germany). The obturated single-rooted-teeth were extracted, multi-rooted-teeth underwent amputation for periodontal reasons. Separated roots were embedded in acrylate. Transversal sections were performed at every 0.5mm up to 2.5mm. Sections were examined under direct, polarized light microscope and stereomicroscope(100X, 500X magnification). Images were captured using digital camera, photos elaborated with Camedia-Olympus-dpsoft-3.1, analyzed using AUTOCAD2002. Data were registered for each section: total perimeter of the canal, instrumented perimeter, perimeter in contact with obturation, total area of the canal, obturated area. Percentage of instrumented perimeter, of obturated perimeter and of obturated areas of the canals were calculated. Spectacular details-anatomical recesses, visible lateral canals, fractures, artifacts, foreign bodies, separated instruments were registrated. Results show increase in mean percentage of instrumented perimeter from 21%(phase 0=apex) to 66%(phase 6=2.5mm), increase in mean percentage of obturated area from 45%(phase 0) to 92%(phase 6) and a surprising slight, continuous decrease of mean percentage of obturated perimeter from 97%(phase 0) to 86%(phase 6). 40.6% of the samples displayed instrumentation, 46.9% displayed obturation on final 0.5mm, separated instruments and foreign bodies were found in 6.25%, 25% of sections displayed anatomical recesses, starting predominantly at 1.5 mm from the apex. Conclusions: Results show satisfactory, yet surprising picture of the outcome of treatment. Data must be refined by diversifying the groups according to tooth type, root shape, curvature, further compared with similar data from in-vitro studies, evaluation should be extended to various root-canal filling-systems. Keywords: root canal obturation, sealing ability, digital analysis