The oldest stars in the Milky Way are metal-poor with [Fe/H][Fe/H]>-3.0). The abundances are derived from spectra obtained with the HRS echelle spectrograph at the Southern African Large Telescope, using both LTE and NLTE approaches, with an average error between 0.10 and 0.20dex. Based on their kinematical properties, we show that HE 1523-0901 and HD 195636 are halo stars with typical high velocities; HD 121135 has a peculiar kinematical behaviour making unclear if it is a halo or an accreted star; and HD 6268 is possibly a rare prototype of very metal-poor thick disk stars. The abundances derived for our stars are compared with theoretical stellar models and with other stars with similar metallicity from the literature.