The Lorentz factor for the Buerger precession method is derived. It turns out that the angular velocity of the motion of the reciprocal lattice through the sphere of reflection is not uniform as hitherto accepted. The Lorentz factor thus depends explicitly on all three cylindrical coordinates &xgr;, &zgr;, &tgr; of the reciprocal lattice point under consideration and not on only as &xgr; and &zgr;.