Influence of wet oxidation on the burning profiles of lignites was investigated. For this purpose, five different Turkish lignite samples were treated with either 0.2 M sodium carbonate solution or distilled water at 423 K under 1.5 MPa partial pressure of oxygen for 60 min. TGA technique was applied to the original and treated lignite samples from ambient temperature to 1223 K under dynamic dry air atmosphere. Burning profiles of the original and treated lignite samples were derived from the thermogravimetric curves. In the case of alkaline conditions, some degradation took place in the organic matrix of the lignite samples. Loss of combustible part of the treated lignite samples led to important changes in the burning profiles of the treated lignite samples compared with those of the original lignite samples. The presence of sodium carbonate was detected from its decomposition peaks, predicting that some of sodium carbonate could not be eliminated from the treated lignite samples. Sulphuric acid forming asa result of the oxidation of sulphur compounds, removed some mineral species from the treated lignite samples, affecting burning profile. Oxidation of the lignite samples in either alkaline or acidic medium increased thermal reactivity. Consequently, the ignition temperature was decreased and burning rates increased. (C) 1999 Elsevier Science B.V. All rights reserved.