Experimental studies demonstrate that atherosclerotic plaques induced in animals can regress following appropriate treatment, but evidence in favour of the regression of atherosclerotic lesions in man is still scanty. New imaging techniques, such as high resolution B-mode echotomography, allow the visualization and measurement of anatomical parameters of the arterial wall in sample arteries of human patients "in vivo", introducing the possibility of a much more precise monitoring of early atherosclerotic lesions. New information on the natural history of atherosclerotic disease in man, including the possibility of differentiating between lesions of different clinical significance, can be expected from the wide application of these techniques to atherosclerosis research. A more precise testing of diets, drugs and physical procedures intended to obtain the regression of atherosclerosis in human beings will also be possible.