The gases and chars produced during fast pyrolysis of maize stalk, rice straw, cotton straw and rice husk at temperatures ranging from 600 to 1000 degrees C were studied by Fourier transform infrared spectroscopy, non-dispersive infrared technique, thermal conductivity detection method, ultimate analysis. X-ray diffraction, helium density measurement and N(2) adsorption method. The gas yield increased by more than 80% from 600 to 1000 degrees C, while the char and liquid yield decreased. The content of CO(2), CO and CH(4) accounted for more than 86%. The CO and CH(4) content increased with temperature, while the CO(2) content decreased. The hydroxyl, aliphatic C-H, carbonyl, olefinic C=C and ether groups were lost above 800 degrees C. Carbon skeleton shrinkage increased by more than 23% when the temperature increased from 600 to 1000 degrees C. Maximum porosity appeared at 900 degrees C. This study revealed the relationships between gas composition/char properties and pyrolysis temperature under high heating rate conditions. (C) 2011 Elsevier Ltd. All rights reserved.