To monitor the dynamical changes in coals with temperature, an in-situ method must be used, therefore, we have applied Single-Point-Imaging and have carried out the first systematic in-situ variable-temperature NMR imaging study of coals between 25 and 500 degrees C with our newly developed high temperature imaging probe and systems. It was found that the distribution of mobile components was very heterogeneous like the distribution of macerals at room temperature. As the temperature became higher, the mobile component started increasing but remained heterogeneous above 400 degrees C and over this the distribution of mobile components became more homogeneous, it is clear that insitu variable-temperature NMR imaging method is very powerful to investigate and clarify the thermal change of coal. (C) 2000 Elsevier Science Ltd. All rights reserved.