Sclerotic involvement of abdominal aorta and lower limb arteries is related to 2 types of fundamental lesions: atherosclerosis and arteriosclerosis. Atherosclerosis is a focal intimal thickening (plaque) of large- and medium-sized arteries, which combines atheroma (lipid deposition) and fibrosis. Plaque rupture is the crucial event in the progression of atherosclerosis, directly causing most acute thrombotic events, and contributing in great part to plaque expansion. Arteriosclerosis is a diffuse fibrosis of the arterial wall with thickening of the intima, and thinning of the media. Two forms of arteriosclerosis probably exist with distinct mechanisms and consequences. Obliterating arteriosclerosis mainly involves leg arteries (causing poor distal run-off) and appears to be essentially enhanced by ageing, diabetes and chronic renal insufficiency. Dilating arteriosclerosis involves large arteries where it provokes aneurysm formation; it is related to ageing, but seems also to be dependent upon an inborn dystrophy of arterial connective tissue. These 3 components of sclerotic arterial diseases of the lower limbs are often combined in the same individual.