A two-part study concerned the accumulation of intravenously injected Evans blue dye in the abdominal aorta of swine. In normolipidemic swine weighing up to 90 kg each, Evans blue accumulated predominantly in areas of the aorta that were the site of intimal smooth muscle cell collections. The second part of the study dealt with Evans blue accumulation in swine with advanced atherosclerosis. The extent of blue staining in these animals was not significantly different than in normolipidemic, nonatherosclerotic swine of the same size. The dye showed a predilection for raised atherosclerotic lesions, but only one quarter of the surface of these lesions was stained. Histologic studies of the uppermost portion of blue and nonblue lesion areas showed that the dye preferentially accumulated in regions with lower concentrations of foam cells. Injected isotopic cholesterol tended to accumulate in the blue rather than the nonblue areas.