Recently, much research has been focused on liquid oil from biomass pyrolysis, which is considered as an alternative to conventional fossil fuels. This paper studies the effect of heating rate on both the yields and the chemical composition of the oil product obtained from pyrolysis of esparto which is the most important biomass in Morocco. The pyrolysis experiments of esparto was performed in a fixed bed reactor under argon atmosphere with different heating rate: 50, 150 and 250 degrees C min(-1). The maximum conversion of esparto in oil of pyrolysis was obtained with fast pyrolysis 68.5% at 550 degrees C. The FT-IR and H-1 NMR analysis showed that the oil of pyrolysis formed principally by aliphatic compound. The analysis elemental showed that the H/C ratio increase and O/C decrease as the heating rate increase. The PCV improved slightly from 33.5 to 34.8 MJ kg(-1). The oil obtained with higher heating rate has chemical properties similar to diesel that can be used with an economic and environmental advantage. Copyright (c) 2006 John Wiley & Sons, Ltd.