An ion and electron multibeam microanalyzer was developed and applied to analysis of coal fly ash particles. Employing ordinary TOF-SIMS function, it was found that the surface of the fly ash particles mainly consisted of Ca, C, Si, and Na. A special analysis technique with a combination of "shave-off" cross-sectioning and TOF-SIMS mapping of the cross section was adopted to a single fly ash particle in order to reveal the internal structure. It was found that the particle had a cenosphere structure. TOF-SIMS mapping of the cross-sectioned particle clarified that the particle had the following layers, outermost layer (Na, Si, Ca-rich), shell (Na-rich), inner shell (Na, Si, Al-rich). (C) 2002 Elsevier Science B.V. All rights reserved.