We report measurements of electron transfer in real space inGaAs/AlxGa1−xAsasymmetric double quantum wells under an electric field by far-infrared cyclotron resonance (CR). Due to nonparabolicity, the asymmetric quantum structure results in well-resolved CR lines, which allow contactless measurements of the electron density in each well. Our results show that electrons tunnel through the barrier from one well to the other at the level anticrossing of their ground states. ©1997 American Institute of Physics.