Atheromatous disease of the arteries is progressive and often results in untimely morbidity and premature death. The pathogenesis of the arterial lesion is as complex as its rate of progression is variable and ill understood. In six patients undergoing coronary arteriography, who were being restudied before percutaneous transluminal coronary angioplasty, the angiographic appearance deteriorated considerably over a fairly short period (mean 3.6 months). Although early detection and preventive measures have lowered the incidence of atheromatous disease and improved survival in some patients, rapid progression of the disease remains a serious hazard in others, who, as a group, remain at present unidentifiable.