  We review recent experimental and theoretical developments in the study of
the sea quark structure of the proton. In the light quark sector, we analyse
the recent pp and pD Drell-Yan data from the E866/NuSea experiment at Fermilab,
and their implication for the d-bar/u-bar asymmetry in the proton. The current
status of the strange content of the proton, including the possible difference
between strange and antistrange quark distributions and strangeness form
factors, is updated. Finally, we point out the ramifications of non-symmetric
charm and anticharm distributions in the nucleon for HERA event rates at large
x and Q^2.
