The hypothesis that dietary erucic acid may contribute to the pathogenesis of intrahepatic cholestasis of pregnancy has been examined in pregnant rats and hamsters after prolonged feeding of diets containing 25% rapeseed oil rich in erucic acid (40% of fatty acids) or corn oil, without erucic acid. Both dietary oils were well tolerated, although weight gain was 17% to 20% less in unimals receiving rapeseed oil. Rats and hamsters were studied on the last day of pregnancy and compared with age- and diet-matched nonpregnant animals. Histological examination showed no major morphologic abnormalities in liver, heart, kidneys, and adrenals. Similar microscopic deposits of fat were found in the livers and hearts of pregnant hamsters of both dietary groups. Chromatographic analysis of fatty acids in liver, heart, and kidney homogenates of hamsters and in isolated rat liver cells reflected the fatty acid composition of the dietary oils: oleic (18:1) and linoleic (18:2) acids were among the predominant fatty acids. Erucic acid was found in a higher proportion in the heart (14% by weight of total fatty acids) than in the liver (3%) and kidneys (3%) of animals fed rapeseed oil. Bile flow and biliary lipid composition was similar in rats and hamsters fed rapeseed or corn oil. Bile flow tended to be less in pregnant than in nonpregnant animals. Pregnant hamsters fed rapeseed oil tended to have the lowest bile flow. The lithogenic index of bile was slightly decreased in pregnant rats and increased in pregnant hamsters, although these proportional changes were similar for both diets. In all circumstances the lithogenic index remained below a value of 1. Biliary excretion of sulfobromophthalein (BSP) and maximal transport capacity of BSP into bile (BSP Tm) were similar in rats fed rapeseed or corn oil diets. In conclusion, no morphologic or hepatic functional abnormalities attributable to the diet could be detected in animals fed rapeseed oil with a high content of erucic acid, whereas pregnancy induced changes in bile secretion in rats and hamsters, irrespective of the diet administered. These observations are still insufficient to reject the possibility that rapeseed oil rich in erucic acid could be involved in the pathogenesis of intrahepatic cholestasis of pregnancy because dietary erucic acid could interact with a genetic metabolic predisposition to induce a disease that seems to be specific to humans.