The concentrations of hexachlorobenzene (HCB) in adipose tissue were similar for FO and Flb generations in rats fed 20 ppm HCB until 45 weeks of age. Nulliparous females receiving treatment equivalent to the HCB-treated FO generation rapidly accumulated HCB in their fat and, by 13 weeks of age, the residue values coalesced with values in 13-week-old Fla females which had received additional HCB via the placenta and milk. Between 13 and 30 weeks of age, steady-state storage was approached and no significant increase in HCB concentrations occurred through 65 weeks of age. Postlactation dams, that nursed average size second litters had considerably lower concentrations of HCB in their fat than dams weaning no pups, suggesting substantial redistribution and/or elimination of maternal stores during lactation.