BACKGROUND/AIM Any forms of mercury have toxic action on the majority of organs, especially kidneys. The major source of professional exposure to mercury are departments for the production of chlorine which use mercury as catode. The aim of the study was to prove that chronic exposure to elementary mercury low concentrations could cause asymptomatic damages of the kidneys. METHODS A total of 40 workers from the factory ,,HIP Petrohemija" Pancevo, of the mean age 45+/-8 years, who were exposed to the effects of mercury for more than 20 years within the production procedure, and 20 workers from the factory "Panonijaplast" Pancevo, of the mean age 44+/-7 years, who were not exposed to mercury nor to other nephrotoxic agents, were submitted to laboratory analysis, renal function testing, and determination of mercury concentration in urine. Mercury concentration was also measured in the air of working premises of the factory. RESULTS The performed measurements confirmed that the concentrations of mercury at any tested working place in the Department of Electrolysis were not more than the maximally permitted concentration for an 8-hour exposition. In the exposed group (40 examinees) 75% of the examinees had mercury in urine in the concentration < 0.1 micromol/l, while in 25% of them it was 0.1-0.75 micromol/l. In the control group (20 examinees) all of the examinees showed to have < 0.1 mol/l mercury in urine. There was determined a positive corelation between the concentration of mercury in urine and the value of beta2-microglobulin (p < 0.05), as well as between the corrcentration of mercury in urine and gammaGT activity (p < 0.05), and between the concentration of mercury in urine and the value of retinol-binding protein (p < 0.01). CONCLUSION In 25% of the examinees excretion of mercury was significantly higher than in the control group. The frequency of asymptomatic renal tubular lesions and dysfunction of moderate extent were found to be higher in the exposed group than in the control one.