The capability of lead to interfere with the first and/or second phase of enzymatic reaction of biotransformation has been investigated in ten lead workers and in ten controls by studying the steroid hormone sulfation and D-glucaric acid (GA) urinary excretion. No statistical differences have been found for the total amount of urinary steroids, whereas a decrease of about 50% was observed for the sulfated fraction in lead workers. The mean value for the GA excretion in the exposed subjects (1.8 +/- 0.7 mmol/mol creatinine) was significantly lower than in the control group (4.4 +/- 0.8 mmol/mol creatinine). In spite of the small number of investigated subjects, it can be hypothesized that an interaction of lead with sulfotransferase exists. The decreased GA excretion does not prove an altered activity of microsomal enzymes, although inhibition of microsomal activity following lead exposure was previously reported.