In order to determine polarized parton distributions we have made a new NLO QCD fit (in \overline {MS} renormalization scheme) using all experimental data on spin asymmetries measured in the deep inelastic scattering on different nucleon targets. The functional form of such densities is based on MRST2001 results for unpolarized ones. We get for polarization of quarks (at Q²=1 {GeV²}): \Delta u = 0.86, \Delta d= -0.37, \Delta s= -0.04. The total quark polarization is rather big and we obtain: \Delta {\Sigma }=0.45. As a result of our fit we get a₃ =g_A=1.23, the value which is close to the experimental number. With negligible \Delta s and rather big \Delta {\Sigma } (comparable to a₈) the results of our new fit are quite different in character from previous fits.

PACS numbers: 12.38.--t, 13.88.+e, 14.20.Dh