The degree of fatty streaking of the aorta (percentage of the intimal surface that stains red with Sudan IV) in 18 cases of fibrocystic disease of the pancreas was compared with that in 21 control cases of the same age group (6-13 years inclusive). All cases were of the white race. The average percentage of the intimal surface involved with fatty streaks was over four times as great in the control group as in the group with fibrocystic disease. The metabolic abnormalities in cystic fibrosis of the pancreas are reviewed in an attempt to discover the mechanism whereby atherosclerosis of the aorta is suppressed. The low levels of most lipids and of chloride in the blood in this disease are pointed out, but in view of the complexity of both fibrocystic disease and atherosclerosis no satisfactory conclusions as to their relationship were attained. Regardless of the ultimate interpretation of these data, fibrocystic disease of the pancreas appears to be the first human disease with decreased atherosclerosis to be documented.