  A next-to-leading order QCD analysis of spin asymmetries and structure
functions in polarized deep inelastic lepton nucleon scattering is presented
within the framework of the radiative parton model. A consistent NLO
formulation of the $Q^2$-evolution of polarized parton distributions yields two
sets of plausible NLO spin dependent parton distributions in the conventional
$\overline{\rm{MS}}$ factorization scheme. They respect the fundamental
positivity constraints down to the low resolution scale
$Q^2=\mu^2_{NLO}=0.34\,{\rm{GeV}}^2$. The $Q^2$-dependence of the spin
asymmetries $A_1^{p,n,d}(x,Q^2)$ is similar to the leading-order (LO) one in
the range $1\le Q^2\le 20\,{\rm{GeV}}^2$ and is shown to be non-negligible for
$x$-values relevant for the analysis of the present data and possibly
forthcoming data at HERA.
