We have measured the electroabsorption in low-temperature grown GaAs by performing room-temperature transmission experiments in the spectral range from 1.3 to 1.9 eV for different electric fields induced by a voltage applied to a metal-semiconductor-metal structure. The devices were separated from the substrate by using an epitaxial liftoff technique. Therefore, we have been able to observe the electro-optic effect at the fundamental band gap as well as at the split-off band edge. The absorption is clearly polarization dependent at the fundamental bandgap but only weakly at the split-off band gap, in agreement with the theory of the Franz-Keldysh effect. (C) 1996 American Institute of Physics.