A voltammetric method for the determination of mercury in domestic waste, compost produced from it and in water extracts of these samples is described. The solid samples have been digested with concentrated acids and the extracts by UV irradiation. Conditions for the voltammetric determination of mercury with a gold disc electrode in samples of very complicated composition have been worked out. To avoid the disturbing influence of copper a special potential — time program has been applied, whereas the disturbing effect of iron has been removed by complexation of Fe(III) with fluoride ions or by medium exchange. The procedure proposed suits very well for determination of mercury in the samples studied. A very low leachability of mercury from compost was found.