Mammalian cell cultures were used to determine the capacity of antidotes to modify (a) lead uptake, (b) lead toxicity and (c) lead release from cells. The following chelating agents were tested: Na, Ca-ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitriloacetic acid, ethylene glycol-bis(aminoethyl)tetraacetic acid (EGTA), D,L-mercaptosuccinic acid (MSA), meso-2,3-dimercaptopropanesuccinic acid (DMSA), D,L-2,3-dimercaptopropane-1-sulfonic acid (DMPS), penicillamine (PA), N-acetylpenicillamine (NAPA), and diethylcarbodithioate (DDTC). The following vitamins were tested: thiamine (B₁), riboflavine (B₂), pyridoxine (B₆), cobalamin (B₁₂) and ascorbic acid (C). Inhibition of lead uptake was produced by EDTA, EGTA, DMSA, DMPS, MSA, PA, NAPA and vitamins B₁, B₆ and C, vitamins B₂ and B₁₂ being ineffective. The same compounds reduced lead cytotoxicity. Interestingly DDTC and DTPA increased lead uptake, but did not exacerbate lead toxicity. Significant release of lead from preloaded cells was caused by DTPA, NAPA, DMPS and PA, while the other chelators were ineffective.