The polychlorinated biphenyls (PCBs) have been demonstrated to be inducers of hepatic microsomal enzymes and some of their effects such as hormonal imbalance, and alteration of lipid and porphyrin metabolism could be ascribed to this mechanism. For this reason, the urinary excretion of D-glucaric acid (DGA), an indirect indicator of enzymatic induction, was suggested as a biological marker of effect following exposure to PCBs. The aim of the present study was to investigate whether any inductive effects resulting from exposure to these compounds through ingestion of contaminated food could be detected early by measuring urinary DGA (U-DGA). U-DGA was measured in 73 subjects exposed to PCBs due to ingestion of PCB-contaminated food and levels ranged from 1.7 to 12.4 mmol/mol creatinine, with a mean value of 5.96 mmol/mol creatinine. These values were higher than those usually found in the general population. Sex and smoking habits did not affect U-DGA excretion, while age and alcohol intake were significantly correlated with U-DGA excretion, a finding in agreement with the results of other investigations. Neither total PCB blood concentration nor PCB chlorine content was significantly correlated with U-DGA excretion, and only the PCB 138 congener was weakly correlated with U-DGA levels. The results indicate that, for exposure to PCB resulting in blood concentrations up to 394 microg/l, no statistically significant effect of these persistent organochlorine compounds on human enzyme induction could be demonstrated, as measured by DGA urinary excretion.