  We report for the first time Na and O abundances from high-resolution, high
S/N echelle spectra of 20 red giants in NGC 2808, taken as part of the Science
Verification program of the FLAMES multi-object spectrograph at the ESO VLT. In
these stars, spanning about 3 mag from the red giant branch (RGB) tip, large
variations are detected in the abundances of oxygen and sodium, anticorrelated
with each other; this is a well known evidence of proton-capture reactions at
high temperatures in the ON and NeNa cycles. One star appears super O-poor; if
the extension of the Na-O anticorrelation is confirmed, NGC 2808 might reach O
depletion levels as large as those of M 13. This result confirms our previous
findings based on lower resolution spectra (Carretta et al. 2003) of a large
star-to-star scatter in proton capture elements at all positions along the RGB
in NGC 2808, with no significant evolutionary contribution. Finally, the
average metallicity for NGC 2808 is [Fe/H]= -1.14 +/- 0.01 dex (rms=0.06) from
19 stars.
