This work contributes to detection and tracking of walking or running humans in surveillance video sequences. We propose a 2D model-based approach to the whole body tracking in a video sequence captured from a single camera view. An extended six-link biped human model is employed. We assume that a static camera observes the scene horizontally or obliquely. Persons can be seen from a continuum of views ranging from a lateral to a frontal one. We do not expect humans to be the only moving objects in the scene and to appear at the same scale at different image locations.