VLT-UVES high resolution spectra of seven turnoff stars in the metal-poor globular cluster NGC 6397 have been obtained .
Atmospheric parameters and abundances of several elements ( Li , Na , Mg , Ca , Sc , Ti , Cr , Fe , Ni , Zn and Ba ) were derived .
The mean iron abundance is [ Fe/H ] = -2.02 , with no star-to-star variation .
The mean abundances of the alpha-elements ( Ca , Ti ) and of the iron-peak elements ( Sc , Cr , Ni ) are consistent with abundances derived for field stars of similar metallicity .
Magnesium is also almost solar , consistent with the values found by Idiart & Thévenin ( 2000 ) when non-LTE effects ( NLTE hereafter ) are taken into account .
The sodium abundance derived for five stars is essentially solar , but one object ( A447 ) is clearly Na deficient .
These results are compatible with the expected abundance range estimated from the stochastic evolutionary halo model of Argast et al .
( 2000 ) , in which at the epoch of [ Fe/H ] \sim -2 the interstellar medium is supposed to become well-mixed .