The cyclotron resonance of a two-dimensional electron gas in an InAs quantum well sandwiched between two GaSb layers has been investigated experimentally for its dependence on the magnetic field. Both the amplitude and the half-width of the resonance show a strong oscillatory behavior, exhibiting a maximum amplitude and correspondingly a minimum half-width when the highest occupied Landau level is half filled. Oscillations for more than ten periods have been observed. From our experiments we can deduce that there is a considerable overlap of the Landau levels, which strongly increases with decreasing magnetic field. © 1986 The American Physical Society.