The influence of lead exposure on renal function was examined. In 155 lead workers and 126 control workers, lead in blood (PbB) and zinc protoporphyrin in blood (ZPP) were measured as indicators of exposure to lead; various proteins in urine were measured as parameters of renal functions. Regression and matched-pair analyses suggest that tubular parameters may be more influenced by lead exposure than glomerular parameters. Changes in renal function parameters may already occur at PbB levels below 3 μmol/liter (600 μg/liter). The excretion of N-acetyl-β-D-glucosaminidase appears to be the most consistent and sensitive parameter of an early effect on the tubular function.