was no intimal thickening of the aortic arch similarly in the presence of 10 a 2 with no dietary cholesterol group 10 or with dietary cholesterol and 5 or 20 a 2 groups 6 and 8 the mean intima to media ratio was 0 group 7 10 a 2 with dietary cholesterol had a mean intima to media ratio of only 0 01 with four of the six rabbits having 0 all a 1 groups both with and without dietary cholesterol had higher intima to media ratios than groups fed a 2 casein and had intima to media ratios not significantly different from group 2 20 whey with 0 5 cholesterol indeed 10 a 1 in the absence of dietary cholesterol produced the same intima to media ratio as 20 whey with 0 5 whey with 0 5 dietary cholesterol 0 03 thus in relation to the thickness of fatty streak lesions in the aortic arch a 1 casein even in the absence of dietary cholesterol produces lesions similar to that produced by 0 5 cholesterol in contrast a 2 both in the presence and absence of dietary cholesterol appears to be highly atheroprotective balloon catheter injury to the right carotid artery t 0 induced a hyperplastic neointimal thickening in all rabbits by 6 week measurement of intima to media ratios showed there was a slight but not significant increase in neointimal thickening in group 2 rabbits 20 whey with 0 5 cholesterol compared with group 1 20 whey alone.