This paper reports the studies made on the vacuum pyrolysis of deashed sugarcane bagasse, on the pyrolysis products. The present work is with an objective to understand the change in the quantity and quality of the oil fraction obtained from pyrolysis, upon pretreatment for deashing of original biomass. Ash, in the entrained char is believed to be catalyzing the polymerization reaction in the oils and thereby increases the viscosity. Three different pre-treatment processes used for deashing are water leaching, mild acid treatment with HCl and mild acid treatment with HF.(1) The study indicates the remarkable influence of pretreatment process for deashing, by enhancing the total energy distribution in oil fraction of the pyrolysis products. This is attributed to selective removal of ash elements along with removal of extractives and hemicellulose in different proportions. However, it was found that the pre-treatments do not improve the stability of oil. The water leachate, as expected, showed potential of making ethanol via fermentation. (C) 2004 Elsevier Ltd. All rights reserved.