This paper reports the evolution of the composition of bio-oil obtained from the fast pyrolysis of Mallee woody biomass as a function of temperature between 350 and 580 °C. Several analytical techniques were used to quantify bio-oil composition. For the volatile components, the results obtained by gas chromatography−mass spectrometry and Karl Fischer titration agree very well with those obtained by thermogravimetric analyses. However, for the heavy components, especially lignin-derived oligomers, synchronous UV-fluorescence spectroscopy and thermogravimetric analysis give more reliable results than the precipitation in cold water. Our results indicate that the accuracy of the precipitation methods to quantify lignin-derived oligomer in bio-oil is limited by the relatively large amounts of small oligomers remaining soluble in a metastable form in cold water. A maximum in the yield of lignin-derived oligomers was observed between 450 and 500 °C. In fact, most of the increases in the yield of bio-oil with in...