The effects of the chelating agents Na2Ca-ethylendiaminetetraacetate (EDTA), Na3Ca-diethylentriaminepentaacetate (DTPA), L-cysteine, 2,3-dimercaptosuccinic acid (DMSA), N-acetyl-L-cysteine (NAC), glutathione, D,L-penicillamine (D,L-PEN) and 2,3-dimercaptopropanol (BAL) on the toxicity, distribution and excretion of intraperitoneally injected cobalt were studied in male Swiss mice. To determine the effect of the various chelators on the toxicity of cobalt, various doses of CoCl2 (0.60-1.80 mmol/kg) were given, followed immediately by the IP administration of the chelator (at a dose equal to one-fourth of their respective LD50). EDTA and DTPA were the most effective. EDTA, DTPA and L-cysteine, NAC and glutathione were also the most effective in increasing the urinary excretion of cobalt and reducing the concentration of the metal in various tissues. EDTA appears to be the most effective agent of those tested in the prevention of acute cobalt intoxication.