  We investigate statistical equilibrium of Cr in the atmospheres of late-type
stars. The main goal is to ascertain the reason for a systematic abundance
discrepancy between Cr I and Cr II lines, which is often encountered in
spectroscopic analyses of metal-poor stars. Up to now, all these studies relied
on the assumption of local thermodynamic equilibrium (LTE) in the spectrum
modelling. For the first time, we perform NLTE calculations in subdwarfs and
subgiants of different metallicities. We show that the LTE assumption is
inadequate to describe excitation-ionization equilibrium of Cr I/Cr II in
stellar atmospheres and, as a result, leads to large errors in abundances. In
particular, the NLTE abundance corrections to Cr I lines range from $+0.3$ to
$+0.5$ dex at low [Fe/H]. The NLTE [Cr/Fe] trend in the halo and the disk is
flat and can be reproduced by most of the models of Galactic chemical evolution
with standard prescriptions for Cr and Fe nucleosynthesis.
