Rigid exclusion of essential fatty acids from the diet of young swine leads to a deficiency disease not characterized by consistent or early skin lesions. The severity of the dietary regime imposed caused high mortality, but of the 8 pigs that survived beyond the normal weaning age, skin lesions were observed in one and aortic lesions in five, at or before 98 days. The lesions were calcifications of the inner third of the media. Essential fatty acids are probably required by swine and deficiency of essential fatty acids may lead to impairment of the arterial wall.