Two patients had heavy metal intoxication resulting from industrial exposure to mercury vapors. One patient remained asymptomatic despite high urinary mercury levels. The second presented with a documented toxic reaction, including abnormal electromyograms and hematuria. Treatment was begun with 2,3-dimercaptopropane-1-sulfonate, an investigational drug used under Food and Drug Administration guidelines (IND 19 276). Use in both patients resulted in a dramatic change in excretion half-life of the mercury, from 33.1 days before treatment to 11.2 days during therapy. No significant toxic effects related to drug therapy were observed. Clearing of hematuria and reversal of electromyographic abnormalities were prompt in the symptomatic patient. Therapy with 2,3-dimercaptopropane-1-sulfonate was effective in these two patients.