An on-line microwave digestion system for the determination of total mercury in solid environmental samples was developed. The slurried samples were injected into a carrier stream of hydrochloric acid and mixed with a solution of potassium bromide–bromate before passing through a PTFE coil situated in the microwave cavity of the microwave digester. During the microwave digestion process, the mercury species were liberated from the sample matrix and full oxidation of organomercury compounds to Hg^II was achieved. After mixing with a solution of hydroxylammonium chloride, to remove the excess of bromine, the determination of mercury was undertaken by on-line cold vapour atomic fluorescence spectrometry. The developed system offers a rapid and sensitive method for the determination of mercury in solid environmental samples with a sample processing time of 50 s and a limit of detection of 13 ng l^–1. In addition, a batch method utilizing open focused microwave digestion, in which samples were digested with a mixture of hydrogen peroxide and nitric and sulfuric acids, was developed. Both methods were validated using the National Research Council Canada certified reference materials DORM-2 and PACS-1 and gave results in good agreement with the certified values.