1. (+)-Penicillamine in a dose of 193 mumoles/kg given subcutaneously twice a day on the sixth and seventh days after the administration of 100 mug mercury increased the urinary excretion of rats more than the equimolar dose of N-acetyl-(+)-penicillamine but less than 2,3-dimercaptopropanol 48.3 mumoles/kg.2. Sodium maleate in a dose of 156 mumoles/kg given on the sixth and seventh days after the mercury did not influence mercury excretion or redistribution. Sodium maleate in the same dose increased considerably the effect of (+)-penicillamine on the urinary excretion and redistribution of mercury. It increased the effect of N-acetyl-(+)-penicillamine only slightly. There was a tendency to decrease the effect of 2,3-dimercaptopropanol.3. All the complexing agents decreased the kidney content of mercury and increased the liver and blood concentration of mercury. These changes were highest with 2,3-dimercaptopropanol. The combination of sodium maleate with (+)-pencillamine caused higher mercury excretion and lower kidney content but a smaller increase in the liver and blood mercury contents than 2,3-dimercaptopropanol.