A SIGNIFICANT parameter for pulsars for which proper motion data are available is the angle φ between the space velocity vector and the spin axis. There are eleven such pulsars (ref. 15 and personal communication from one of the authors). The angle between the spin axis projected on the plane of the sky and the proper motion vector has a value close to 0° for three of them, close to 90° for six and between 0° and 90° for the remaining two. We present here a hypothesis which would explain how the different orientations of the space velocity vector relative to the spin axis arise. We distinguish between three modes of formation of pulsars and show that these correspond to the three different sets of values of the angle.