The time dependence of organ distribution and excretion of intravenously (iv) injected 210Po was investigated after the single or repeated administration of N,N'-diethylamine-N-carbodithioate (diethyldithiocarbamate, DDTC) and three bis-dithiocarbamates: N,N'-dimethylethylenediamine-N,N'-biscarbodithioate (MeTTC), N,N'-diethylethylenediamine-N,N'-biscarbodithioate (EtTTC), and N,N'-di)20hydroxyethyl)ethylenediamine-N,N'-biscarbodithioate++ + (HOEtTTC). The biokinetics of iv injected 210Po was used as a model for the behaviour of 210Po absorbed into the blood from any other site of entry into the body. The most effective chelating agent was HOEtTTC, which was not only effective when injected subcutaneously (sc) immediately after 210Po, but also 1 h later. Toxic effects of DDTC were observed in a metabolic study when the effect of HOEtTTC was compared with that of DDTC. DDTC caused accumulation of 210Po in brain and transiently in liver. When HOEtTTC was administered, the faecal excretion of 210Po was increased from the very beginning. MeTTC, EtTTC and N-(2,3-dimercaptopropyl)phtalamidic acid (DMPA) were ineffective when the treatment started 1 h after iv injection of 210Po.