  We study deep inelastic scattering on isospin asymmetric nuclei. In
particular, the difference of the nuclear structure functions and the Gottfried
sum rule for the lightest mirror nuclei, 3He and 3H, are investigated. It is
found that such systems can provide significant information on charge symmetry
breaking and flavor asymmetry in the nuclear medium. Furthermore, we propose a
new method to extract the neutron structure function from radioactive isotopes
far from the line of stability. We also discuss the flavor asymmetry in the
Drell-Yan process with isospin asymmetric nuclei.
