When polarized light passes through a material in the presence of a st
rong magnetic field, birefringence is observed. This is known as the C
otton-Mouton effect. Owing to the increasing sophistication of both ex
perimental and computational techniques, this particular aspect of mag
neto-optics has been investigated increasingly in the last few years.
In this review the basic facts concerning both experiment and theory a
re discussed and tables summarizing all currently known gas-phase data
are presented.