Far-infrared magneto-transmission studies are reported on GaSb/InAs/GaSb quantum wells using circular polarized light. Electron and hole Landau level transitions are observed and identified by their selection rules. The effective masses and densities of both kinds of carriers are determined as a function of magnetic field and the InAs layer thickness. We find that the hole cyclotron resonance disappears at high magnetic fields due to depopulation of the holes when the ground hole Landau level crosses the Fermi level. © 1988.