A review with 34 refs. covering Hg and selected compounds, concentrations of Hg in natural waters, in the atmosphere, In plants, fish, human hair, organs and body fluids, maximum permissible concentrations in foodstuffs, poisoning of humans with Hg (Minamata disease), extreme concentrations (Iraq, Amazonia), and an automatic analyzer (Nippon Instruments Corp.'s Automatic Mercury SP-3D Analyzer) enabling Hg to be determined in fuels (e.g., in naphtha) by the Union of Petrol Producers Method 938-95 (French Petroleum Institute).