The BAHA (bone-anchored hearing aid) is a bone conduction hearing aid with percutaneous transmission of sound vibrations to the skull. The device has been thoroughly evaluated by various implant groups. These studies showed that, in audiological terms, the BAHA is superior to conventional bone conduction devices. In comparison with air conduction devices, the results are ambiguous. However, a positive effect is found with respect to aural discharge. The most powerful BAHA can be applied to patients with a sensorineural hearing loss component of up to 60 dB HL. It was shown that bilateral BAHA application leads to binaural sound processing. Preliminary results on the application of the BAHA in patients with unilateral conductive hearing loss suggest that stereophonic hearing can be re-established. The application of the BAHA as a transcranial CROS (contralateral routing of signal) device in unilateral deafness minimizes head shadow effects.