In this paper we describe method for calibrating a stereo pair of cameras using general or planar motions. The method consists of upgrading a 3-D projective representation to affine and to Euclidean without any knowledge neither about the motion parameters nor about the 3-D layout. We investigate the algebraic properties relating projective representation to the plane at infinity and to the intrinsic camera parameters when the camera pair is considered as a moving rigid body. We show that all the computations can be carried out using standard linear resolutions techniques. An error analysis reveals the relative importance of the various steps of the calibration process: projective-to-affine and affine-to-metric upgrades. Extensive experiments performed with calibrated and natural data confirm the error analysis as well as the sensitivity study performed with simulated data.