Ten men aged 56 to 84 were hospitalized with a diagnosis of periarteritis nodosa, whereas they had multiple cholesterol embolism. The diagnosis was corrected post mortem in the first 3 patients and subsequently in live patients. The particularly misleading clinical manifestations were neurological (polyneuritis in 5 cases, mononeuritis in 1, central nervous system disorders in 3), pulmonary (alveolar haemorrhage in 2 cases, respiratory failure of unknown mechanism in 4) and pericardial (2 cases). Five patients had eosinophilia (more than 500 eosinophils/mm3). The elements that led to the correct diagnosis were the presence of vascular risk factors in all 10 patients (but hyperlipidaemia in only one), severe complications of the atheromatous disease in all cases, a precipitating or aggravating factor in 8 patients (anticoagulant therapy in 7, arteriography in 6) and the finding of purple or necrotic toes (6 cases). Histological (5 cases) and/or ophthalmological (2 cases) evidence was obtained in only 6 patients. Seven patients died 1 to 3 years after the onset of the disorders. Studies on low-density lipoprotein metabolism are in progress to determine the mechanism of clinical manifestations unexplainable by embolism.