The present study investigated the effects of single (lx) administration and a 10-day treatment with chelidonine (50 and 100 mg/kg i.p.) or drug Ukrain (7 and 14 mg/kg i.p.) on the ß2-microglobulin concentration in the serum of acute or subacute lead-poisoned rats (30 mg/kg i.p.). Both acute and subacute lead-intoxication significantly enhanced ß2- microglobulin concentration in the rats serum in comparison to the control groups. In acute poisoning only chelidonine (100 mg/kg i.p.) significantly decreased ß2-microgIo- bulin concentration in the rat serum. In subacute lead intoxication, 10-day treatment with chelidonine (50 mg/kg i.p.) or Ukrain (14 mg/kg i.p.) significantly decreased ß2- microglobulin in the serum of rats. Both chelidonine as well as Ukrain decreased nefrotoxicity induced by lead acetate. These investigations are to be continued.