Vertexing strategy and algorithms at ATLAS

The A Toroidal LHC ApparatuS (ATLAS) inner detector consists of three layers of silicon pixels, four double layers of silicon microstrips and a transition radiation tracker (straw tubes). The good performance of the charged track reconstruction and the vertexing possibilities are determined in large part by the small radius, fine pitch and low occupancy of the innermost component: the pixel detector. The strategy for the track and vertex reconstruction, both at trigger level and offline, are reviewed and the most relevant algorithms discussed. Results, from full detector simulation, are presented on track and vertex reconstruction efficiencies and resolutions and on the b-tagging capabilities.