Contra lateral routing of signals (CROS) using hearing aids and bone conduction devices has been the conventionally accepted modality for the treatment of single sided hearing impairment. The CROS hearing aid has been found to improve speech understanding in noise, when the signal-to-noise ratio is more favourable at the impaired ear than the non-impaired ear. However, the indiscriminate routing of signals to a single ear has practical detrimental effects when interfering sounds are located on the side of the impaired ear. Recently several reports have suggested that cochlear implantation in single sided hearing impairment can restore access to the binaural cues which underpin the ability to localise sounds and segregate speech from other interfering sounds. The current article reports on a prospective trial which has started recruiting and is designed to assess the efficacy of cochlear implantation, compared to a CROS hearing aid in restoring binaural hearing in adults with acquired single-sided deafness. The patients will be assessed at baseline and after receiving a CROS hearing aid. A cochlear implant will be provided to those patients who do not receive sufficient benefit from the hearing aid. The outcome of this trial promises to be interesting and may provide an answer to whether cochlear implantation will replace CROS devices as the standard of care in single sided hearing impairment.