Carotid atherosclerosis is the most common life-threatening neurological disease and therefore an accurate assessment of atheromatous plaques is clinically important. Several studies were developed to characterize plaques from two-dimensional (2D) ultrasound images that are associated with high risk of stroke. However, 2D characterization may not be very accurate because it depends on the selection of a representative ultrasound image of the plaque by an experimented physician. In this paper we present a novel approach for diagnosis based on 3D ultrasound, which only requires a common ultrasound equipment without need of any additional and expensive devices like spatial locators. The semi-automatic algorithm uses medical guidance to obtain a 3D representation of the carotid artery and plaque and automatically generates measures to characterize the plaque in terms of dimensions and texture. A useful analysis tool is provided to allow the identification of vulnerable foci within the pla...