A range of indicators is available to assess renal dysfunction in lead exposure. This study was undertaken to find out which indicators were most valuable as markers of renal dysfunction. We selected 75 male workers from the secondary lead smelter, plastic stabilizer and radiator manufacturing industries (the "exposed" group) and 64 male office workers (the "control" group). Blood lead; blood zinc protoporphyrin; urine lead; urine coproporphyrin; delta-aminolevulinic acid dehydratase activity; and urine delta-aminolevulinic acid were chosen as indicators of lead exposure. Blood urea nitrogen; serum creatinine; serum uric acid; urine N-acetyl-beta-D-glucosaminidase; urine albumin; urine alpha1-microglobu-lin; and urine beta2-microglobulin were used as indicators of renal dysfunction. Urine alpha1-microglobulin level was significantly associated with, the lead exposure level. Blood urea nitrogen, urine N-acetyl-beta-D-glucosaminidase and urine alpha1-microglobulin levels were highly correlated with indicators of lead exposure. Urine alpha1-microglobulin had the highest correlation with other indicators of renal function. In addition, the proportion of subjects with high urine alpha1-microglobulin levels showed a gradient with lead exposure. Conclusively, Blood urea nitrogen, urine N-acetyl-beta-D-glucosaminidase and urine alpha1-microglobulin are useful indicators, but urine alpha1-microglobulin is ; the early 'and the most valuable indicator of renal dysfunction related to lead exposure.