Context :

Aims : We investigate statistical equilibrium of Cr in the atmospheres of late-type stars to show whether the systematic abundance discrepancy between Cr I and Cr II lines , as often encountered in the literature , is due to deviations from LTE .
Furthermore , we attempt to interpret the NLTE trend of [ Cr/Fe ] with [ Fe/H ] using chemical evolution models for the solar neighborhood .

Methods : NLTE calculations are performed for the model of Cr atom , comprising 340 levels and 6806 transitions in total .
We make use of the quantum-mechanical photoionization cross-sections of Nahar ( 2009 ) and investigate sensitivity of the model to uncertain cross-sections for H I collisions .
NLTE line formation is performed for the MAFAGS-ODF model atmospheres of the Sun and 10 metal-poor stars with -3.2 < [ Fe/H ] < -0.5 , and abundances of Cr are derived by comparison of the synthetic and observed flux spectra .

Results : We achieve good ionization equilibrium of Cr for the models with different stellar parameters , if inelastic collisions with H I atoms are neglected .
The solar NLTE abundance based on Cr I lines is 5.74 dex with \sigma = 0.05 dex ; it is \sim 0.1 higher than the LTE abundance .
For the metal-poor stars , the NLTE abundance corrections to Cr I lines range from +0.3 to +0.5 dex .
The resulting [ Cr/Fe ] ratio is roughly solar for the range of metallicities analyzed here , which is consistent with current views on production of these iron peak elements in supernovae .

Conclusions : The tendency of Cr to become deficient with respect to Fe in metal-poor stars is an artifact due to neglect of NLTE effects in the line formation of Cr i , and it has no relation to peculiar physical conditions in the Galactic ISM or deficiencies of nucleosynthesis theory .