Hexachlorobenzene (HCB) was administered at dose levels of 0, 1.0, 10.0, or 50.0 mg HCB/kg body wt by gavage to pregnant hamsters and guinea pigs for 6 days up to the time of liver development in the fetus. Samples of maternal fat, thymus, skin, liver, lung, brain, spleen, urinary bladder, muscle, plasma, and blood were analyzed for HCB concentration. Additionally, fetuses, placentas, and yolk sacs were analyzed for HCB content. HCB was found in all tissues assayed. The highest concentrations of HCB were found in the hamster tissues, with the hamster fetuses having a fivefold greater concentration of HCB than the guinea pig fetuses. Comparisons were made of the hamster and guinea pig data with similar data in the mouse and rat.