Aortic root abnormalities (atherosclerotic thickening and obstruction) seen at necropsy may readily be detected by aortography in familial hypercholesterolaemia. We studied 35 patients with familial types IIa and IIb hyperlipoproteinaemia including three homozygotes and 32 heterozygotes. Two homozygotes showed abnormal bright echoes (atheroma) encircling the proximal aortic root, which interfered with full excursion of the aortic cusps. One homozygote showed the typical echocardiographic features of supravalvular aortic stenosis at the superior border of the sinus of Valsava with normal aortic cusps. Cardiac catheterisation showed valvular gradients of 15 and 80 mm Hg in two homozygotes and a supravalvular gradient of 40 mm Hg in the third. Left coronary artery ostial stenosis was identified by echocardiography in all three homozygotes. Echocardiographic measurements of the aortic root in the 32 heterozygotes were similar to the control group, but 10 patients showed abnormal bright echoes within the aortic cusps and four had supravalvular changes similar to, but less severe than, the homozygotes. In one severely heterozygote supravalvular atheroma prevented full aortic cusp excursion, and this finding was confirmed during coronary artery bypass surgery.