The aim of this study was to evaluate the efficacy of meso-2,3-dimercaptosuccinic acid (DMSA) treatment in workers with increased lead absorption and no overt symptoms of lead poisoning. Seven occupationally lead exposed male workers with blood lead concentrations (PbB) exceeding 50 micrograms/100 ml and a positive calcium disodium ethylenediaminetetraacetate (EDTA) lead mobilization test were treated with DMSA for 19 days. Individual doses were 700 mg DMSA, three times a day from day one to five, and twice a day from day six to 19. The treatment intensified urinary lead excretion, most rapidly during the first five days. The increased elimination was followed by a decline of mean PbB to 15% of the pretreatment values. However, 15 days after the treatment, the PbB concentrations rebounded, yet kept below the baseline values and did not exceed 40 micrograms/100 ml. After repeated EDTA lead mobilization test, urine lead was 23-68% of that before DMSA treatment. It can be concluded that DMSA can effectively reduce chelatable lead in occupationally exposed workers.