The main objective of the present work was to study the pyrolysis under vacuum of sugarcane bagasse combined with petroleum residue (PR), in terms of yields and properties of the products obtained. Important synergetic effects were observed during the co-pyrolysis in a fixed bed reactor leading to an increase in charcoal yield. Maximum charcoal and minimum oil yields were obtained with 15 wt% of PR mixed with bagasse. At this concentration, sugarcane bagasse charcoal is almost completely covered with PR-derived pyrolytic carbon. At concentrations higher than 15 wt%, hydrocarbon vapours interacted less with the bagasse charcoal. Consequently, an appreciable increase in oil yield was observed. The oils obtained are complex emulsions, which consist of oxygenated compounds originating from bagasse, hydrocarbons originating from PR and water. Oils obtained from feedstock with concentrations up to 15 wt% PR are stable emulsions consisting of PR-derived products in bagasse-derived oil. The oil obtained from the 30 wt% PR-bagasse blend is an unstable emulsion. However, the emulsion obtained at 50 wt% PR is again stable. In this emulsion, the PR-derived oil constitutes a continuous phase. This emulsion exhibits a carbon Conradson residue value (9 wt%) similar to that of PR-derived oil. A detailed characterization of the gas, oil and charcoal co-pyrolysis products is presented. (C) 2002 Elsevier Science Ltd. All rights reserved.