An examination was made of the relative efficacies of 2,3-dimercapto-1-propanol (BAL) and three diesters ( [CH(SH)COOR]2; DMDMS, R = CH3; DEDMS, R = C2H5; and Di-PDMS, R = CH(CH3)2] of meso-2,3-dimercaptosuccinic acid (DMSA) in mobilizing freshly injected lead from mice. These diesters, like BAL, reduced the lead levels resulting from freshly injected lead in both the soft tissues (liver, kidneys, spleen, and brain) and the bone (tibia). After treatment with the dimethyl (DMDMS), the diethyl (DEDMS), and the diisopropyl (Di-PDMS) esters the lead content of each of the organs was significantly less than that present in the untreated controls. Each of the diesters reduced lead levels in the kidneys, liver, and spleen significantly below those levels found after BAL treatment. The action of the diesters in reducing brain lead levels was comparable to that of BAL. Di-PDMS was the most effective of these compounds and was significantly superior to BAL. Each of the esters was also significantly more effective than BAL in reducing the whole body level of lead.