The strong sorption of mercury to humic matter in soil and water has raised the question about the influence of organic matter of different soil types on the mobilization of mercury from soil. Mercury is normally bound to humic and fulvic acids, which may be released in connection with flooding, draining and ditching. High mercury contents in fish from man-made lakes have been reported mainly from temperated regions. This has been assumed to be a result of the slower metabolism of methyl mercury in cool water but the effect of temperature on the mobilization process is still poorly known. The sorption and leaching of mercury in three different soils was studied in vitro using a mercury concentrations near the natural level. Soil lysimeters were watered with distilled water or artificial acid rain at two temperatures.