Small-X Nuclear Effects in Parton Distributions

We summarize the status of nuclear parton distribution functions in nuclei at low x and show that they are not constrained well enough by the available data. Measurements of Drell-Yan dimuon pair production on nuclei at the JHF is singled out as a good candidate to significantly increase information about antishadowing and shadowing of valence and antiquark parton distributions in nuclei. A brief description of the leading twist approach to nuclear shadowing is given and outstanding theoretical problems are reviewed.