  We present NLTE abundances of CNO for a sample of four O9 stars in the
Galaxy, together with new determinations of their stellar parameters, $T_{\rm
eff}$, $\log g$, $\epsilon$(He) and microturbulence. These new analyses take
into account the effect of {\it line--blocking} in the spectral synthesis with
our classical NLTE, plane--parallel and hydrostatic model atmospheres. The
sample includes three O9 He normal stars: two dwarfs, HD 214680 and HD 34078,
and one supergiant, HD 209975, and one fast rotating giant with a preliminary
high He overabundance, HD 191423 with $\epsilon$(He)=0.20. We find first that
the consideration of microturbulence in the spectral synthesis for the fast
rotator leads to a considerably lower He abundance, $\epsilon$(He)=0.12. The
CNO abundances of the three He normal stars are in good agreement with the
values in the literature for Galactic B dwarfs with no evidence of mixing, and
show that they all have the same chemical composition. We also discuss however
the possible CNO contamination of the supergiant HD 209975. For the fast
rotator we find that the abundances show the trend of the CNO contamination: a
N overabundance together with C and O depletion. The N/C and N/O ratios of our
stars as a function of their projected rotational velocities are consistent
with the predictions of the recent evolutionary models of Meynet & Maeder
[Mey&Mae00].
