Several coals were pre-oxidized by air at 250, 270 and 300degreesC to different levels, then the carbonization behaviors of the pre-oxidized coals were systematically examined. The gas formation rates and weight change during the carbonization were measured continuously using a mass spectrometer and a thermogravimetric analyzer, respectively. The changes in the functional groups during the carbonization were measured by an in situ FTIR technique. The micropore distributions of the pre-oxidized coals were measured before and after the carbonization. From these measurements the effect of pre-oxidation on the carbonization or coal was examined in detail. (C) 2002 Elsevier Science Ltd. All rights reserved.