We have derived abundances of O , Na , Mg , Al , Si , Ca , Sc , Ti , V , Cr , Fe , Ni and Ba for 43 metal-poor field stars in the solar neighbourhood , most of them subgiants or turn-off-point stars , with iron abundances [ Fe/H ] ranging from -0.4 to -3.0 .
About half of this sample has not been analysed spectroscopically in detail before .
Effective temperatures were estimated from uvby photometry , and surface gravities primarily from Hipparcos parallaxes .
The analysis is differential relative to the Sun , and carried out with plane-parallel MARCS models .
Various sources of error are discussed and found to contribute a total error of about 0.1–0.2 dex for most elements , while relative abundances , such as [ Ca/Fe ] , are most probably more accurate .
For the oxygen abundances , determined in an NLTE analysis of the 7774 Å triplet lines , the errors may be somewhat larger .
We have made a detailed comparison with other similar studies and traced the reasons for the , in most cases , relatively small differences .

Among the results we note the following : We find [ O/Fe ] to possibly increase beyond [ Fe/H ] = -1.0 , though considerably less than obtained by others from abundances based on OH lines .
We do not trace any tendency for strong overionization of iron .
We find the excesses , relative to Fe and the Sun , of the \alpha elements Mg , Si and Ca to be smaller than those of O .
We discuss some indications that also the abundances of \alpha elements relative to Fe vary and the possibility that some of the scatter around the trends in abundances relative to iron may be real .
This may support the idea that the formation of the Halo stars occurred in smaller systems with different star formation rates .
We verify the finding by Gratton et al .
( 2003b ) that stars that do not participate in the rotation of the galactic disk show a lower mean and larger spread in [ \alpha /Fe ] than stars participating in the general rotation .
The latter stars also seem to show some correlation between [ \alpha /Fe ] and rotation speed .
We trace some stars with peculiar abundances , among those two Ba stars , HD 17072 and HD 196944 , the latter already known to be rich in s elements .
We finally advocate that a spectroscopic study of a larger sample of halo stars with well-defined selection criteria is very important , in addition to the very considerable efforts that various groups have already made .