Male Wistar rats were subacutely treated with sublethal doses of HgCl2, CdCl2, Pb(NO3)2, or Na-aurothiomalate. The metal preparations contained trace doses of radioactive nuclide. Based on the doses given and on the radioactivity excretion in urine and faeces the body burden was determined. After the metal treatment periods, some of the animals received N-acetylcysteine (up to 100 mg/kg daily, on 6 consecutive days, i.p.), and the effect of this potential chelator on metal excretion was monitored. The excretion of Hg (after dosing with HgCl2) was not influenced by N-acetylcysteine. The elimination of Cd in urine (after dosing with CdCl2) was increased by a factor of four. Also, the elimination of Pb [after dosing with Pb(NO3)2] was gradually increased (in faeces and urine) by increasing doses of N-acetylcysteine. After dosing with Na-aurothiomalate, the excretion of Au in urine was increased to about 30%. The data suggest some activity of N-acetylcysteine in facilitating excretion of Pb, Cd or Au, but not of Hg.