The α_S Dependence of Parton Distributions

We perform next-to-leading order global analyses of deep inelastic and related data for different fixed values of $\alpha_S (M_Z^2)$. We present sets of parton distributions for six values of $\alpha_S$ in the range 0.105 to 0.130. We display the $(x, Q^2)$ domains with the largest parton uncertainty and we discuss how forthcoming data may be able to improve the determination of the parton densities.