Mercury in coal and coal ash samples was determined by atomic fluorescence spectrometry after microwave digestion. The validity of the method was studied by spike recovery tests and by analyzing certified reference material. The results obtained for mercury in coal and coal ashes were generally in good agreement with that of the wet digestion method. Moreover, microwave methods generally permitted to reduce considerably the digestion time. Furthermore, the mercury results obtained for coal samples by different acid mixtures microwave method provided valuable information for identifying the modes of occurrence of mercury in coal.