A lens arrangement for transforming a divergent, generally astigmatic laser beam from a diode laser into a beam having a high degree of rotational symmetry is disclosed. The arrangement comprises, in series, a first cylindrical gradient index lens arranged with its principal axes parallel to the principal axes of the astigmatic laser beam; a second cylindrical gradient index lens arranged with its principal axes parallel to the principal axes of the astigmatic laser beam; and a third cylindrical gradient index lens arranged with its principal axes rotated 45 degrees with respect to the principal axes of the astigmatic laser beam. The first and the second gradient index lenses have such refractive powers that both the fast and the slow axis of the astigmatic laser beam are converged to a focus inside the third gradient index lens.