Standardized postmortem samples of thoracic and abdominal aortas from traumatic death victims (aged 15-34 inclusive) were selected according to renal indices of estimated blood pressure. Half of the males had renal small-artery evidence of elevated blood pressure, and half did not. The group consisted of an approximately equal number of black and white males. All of the individuals were nonsmokers and had similar age, cholesterol, and HDL distribution. Lipid deposition in the thoracic and abdominal aorta sections was determined quantitatively by means of computer micromorphometry in sections stained with Oil Red O. Results showed that there is a marked increase in extracellular lipid deposition in the intima for those arteries studied with elevated renal indices of hypertension. In addition, there is significantly more extracellular lipid in the abdominal aortas in black males than in white males. Also notable was the finding that the thoracic aorta samples exhibited significantly thicker intimas and larger intimal areas in the high blood pressure index groups than in the low blood pressure index groups. These results suggest that the development of atherosclerotic lesions may be due to an increased deposition of extracellular lipid in the matrix of the arterial intima.