Fehrenbach’s objective-prism technique for the measurement of radial velocities is well known and has already proved its efficiency. New measuring devices (MESUCOR, FENTOMIX at the O.H.P.) based on the correlation between records make the measurement more rapid and more accurate and will encourage others to use this method. An example is the Hipparcos radial-velocities program. But it is also true that this new process has its limits and does not permit one to get all the information which is on an objective-prism plate, for it is limited by the quality (principally the density) of the images. It will be necessary to continue with the classical visual measurements, especially if one wants to detect faint high-velocity stars quickly, which are often at the density limit of the photographic plate. We must keep in mind that the objective-prism technique is best for this purpose since a three or four hour exposure leads to a great number of spectra (about 60 near the pole, to 200 in the galactic plane in a field of 2X2 degrees).