1. Blood lead and erythrocyte glutathione reductase (GSSG-R) and glucose 6-phosphate dehydrogenase (G6P-D) activities were measured in normal subjects and in those with occupational exposure to lead.
2. With increasing blood lead concentration, GSSG-R activity increases and that of G6P-D decreases.
3. It is suggested that these changes represent part of a compensatory mechanism to overcome the reduction of sulphydryl groups by lead ions.