Ultrasound methods have been used for the vascular examination of middle-aged patients with insulin-dependent diabetes mellitus (IDDM, n = 44) or heterozygous familial hypercholesterolemia (FH, n = 37); they were compared with 50 healthy controls. To define the localization of the early arterial lesions in these two conditions, the determination of ankle pressure by Doppler ultrasound and the detection of flow disturbances in the iliac arteries by echo-Doppler technique have been combined in a single vascular investigation. There were no major differences in mean age, degree of overweight, sex distribution, blood pressure, or smoking habits among the three groups. Total serum cholesterol in patients with FH was almost double compared with diabetics and controls. Triglyceride, HDL cholesterol, and blood pressure values did not differ. Nine of 88 limbs of patients with IDDM had an abnormally low ankle-arm pressure ratio (less than 0.97), and there were three cases of low ratio of 100 limbs in the control subjects (P less than .02). The corresponding figure for heterozygous FH was of three of 74 limbs (not different from controls). Echo-Doppler abnormalities suggesting lesions in the iliac arteries were significantly increased (P less than .01) in FH patients (13 limbs with lesions of 74) compared with controls (four of 100 limbs). The proportion of echo-Doppler abnormalities in IDDM (four of 88 limbs) was practically the same as compared to the controls.