This paper describes a new method for the three-dimensional (3-D) tracking and the quantification of blood vessels from Magnetic Resonance Angiography (MRA). The approach is based on the 3D geometrical moments and consists of the following steps : (1) interactive selection of 3-D seed points ; (2) automatic tracking of the vessels ; (3) local computation of both diameter and orientation ; (4) rendering of the vessels. This detection and estimation scheme has been validated on simulated and real data.