The incremental polarizability which occurs when two nitrogen molecules interact has been calculated by theab initiofinite field SCF method. For the configurations studied the [5s, 4p, 1d] gaussian basis set gives a potential surface which is in qualitative agreement with otherab initioestimates. At separations around the energy minimum the interaction α is well represented by the dipole-induced dipole model. At closer separations the deviations from DID behaviour are qualitively similar to those which occur in rare gas diatoms.