Twenty-five moderately exposed lead workers (mean blood-lead level 1.9 mumol/l) had lower plasma levels of follicle stimulating hormone than 25 individually matched controls without occupational lead exposure (blood-lead level 0.2 mumol/l). In addition, the ten most heavily exposed individuals had higher levels of thyroid stimulating hormone, and the 14 workers under the age of 40 had decreased plasma levels of luteinizing hormone and serum levels of cortisol, as compared to the controls. All values were within "normal" reference limits. There was no significant change of the plasma testosterone level. These data indicate a complex effect on the endocrine system by moderate lead exposure, possibly mediated by changes at the hypothalamic-pituitary level. Besides the effect on hormone levels, there was also a decrease in plasma selenium level for the lead exposed workers.