Oleoylanilide has been related to the etiology of an epidemic of poisoning in Spain from denatured rapeseed oil. Fatty acid composition of phospholipids, production of malondialdehyde, and levels of reduced glutathione have been determined in lung, liver, and kidney after feeding rats with either oleoylanilide or denatured rapeseed oil. The liberation of arachidonic acid, primarily from phosphatidylethanolamine, was concomitant with the increase of malondialdehyde levels and the diminution of reduced glutathione in the denatured oil-fed group of rats. The extent of these effects differs with the tissue. Levels of cytochrome P-450 did not show any variation between the groups.