The proposed shape descriptor is based on the beams originated from a boundary point, which are defined as lines connecting that point with the rest of the points on the boundary. At each point, the angle between a pair of beams is calculated to extract the topological structure of the boundary. Then, a shape descriptor is defined by using the third-order statistics of all the beam angles in a set of neighborhood systems. It is shown that beam angle statistics (BAS) is invariant to translation, rotation, scale and is insensitive to distortions. Experiments are done on the dataset of MPEG 7 Core Experiments Shape-1. It is observed that BAS outperforms the MPEG 7 shape descriptors. (C) 2003 Elsevier Science B.V. All rights reserved.