Left and middle panels: distributions of projected rotational velocities for the O-star sample, based on our determinations for vsini (PF) (extra line-broadening neglected) and vsini (FT+GOF) (extra line-broadening taken into account). In both panels, the binsize is 30 km s^-1, and the contribution of supergiants is highlighted by the shaded area. Right panel: vsini (FT+GOF) versus vsini (PF). Luminosity class I objects are highlighted in dark blue, II and III objects in light blue, and IV and V objects in green. The one-to-one relation is marked by the solid line.