Differently from fossil pitches, wood tar pitches have been very little studied so far as precursors of advanced carbonaceous materials (ACM). However,the development of applications for biopitches is important to increase the revenue of the charcoal manufacturing industry and to stimulate the use of biomass, thereby answering the appeals of environment preservation. This work consists of a pioneer study on Eucalyptus tar pitch, its chemical characterization, and pretreatment aiming toward the production of carbon fibers.. The pretreatment is made to adjust the pitch properties, which are important for the subsequent steps in material processing-and for the final product performance. Fourier transform infrared spectroscopy (FTIR), solid state C-13 NMR, and elemental,analysis show that biopitches are mainly constituted of interlinked phenolic rings, which are highly substituted and oxygenated. Pretreatment involved thermal polymerization. The changes in pitch polymerization degree, structure and properties during pretreatments were assessed using differential scanning calorimetry (DSC), gel permeation chromatography (GPC), thermogravimetry (TG), 13C NMR; and elemental analysis. Moreover, the softening points (SP) and acetone-insoluble contents (AI) were determined. The results showed that polymerization was more effective at higher temperatures (about 250 degreesC) and it was followed by increases in glass transition temperature (T-g), SP, AI, thermal stability, and coke yield. During polymerization, side chains were released giving rise to an increase in pitch aromaticity. The possibility of adjusting wood pitch properties lends them a good perspective as precursors of ACM.