In this study, the effect of mineral matter content on the combustion curve of the chars produced from 25 lignite samples originating from different parts of Turkey was investigated using differential thermal analysis (DTA). During the DTA studies, original and demineralized lignite samples were carbonized under identical conditions in nitrogen atmosphere up to 1423 K and, after cooling to the room temperature under nitrogen flow, they were heated at a constant rate of 40 K min(-1) in flowing air up to 1273 K. The DTA combustion curves of the char samples produced from the original and demineralized lignites and their heat release rates are compared and discussed. It was observed that the shapes of the DTA combustion curves of the chars were strongly affected by the demineralization process. In particular, the burn-out times and the heat release rates changed markedly.