Renal function was studied in 40 workers chronically exposed to lead at a smelter. The geometric means of lead were 40 (range 24.0 - 63.0) micrograms/dl in blood and 47 (range 19 - 115) micrograms/g creatinine or 71 (range 20 - 250) micrograms/l in urine, respectively. There were no significant differences between the lead-exposed group and a control group in the concentrations of beta 2-microglobulin in serum, urinary total protein and IgG, whereas the level of beta 2-microglobulin in urine was significantly higher in the lead-exposed group (p less than 0.01). No individual lead worker showed abnormally increased level of urinary beta 2-microglobulin. The significance of increased excretion of beta 2-microglobulin on the basis of the group remains to be elucidated.