Adult unilateral hearing loss is a frequent complaint observed by the E.N.T. specialist. With a pure tone audiometry, we can recognize a conductive hearing loss from a sensorineural hearing loss. In case of a conductive hearing loss, a temporal bone computed tomography is the first choice procedure. For the sensorineural hearing loss, the standard screening test is the brainstem evoked response auditory (BERA), which can be completed by a magnetic resonance imaging (MRI). The BERA have a false negatives level of 2 to 15% according to the studies, which means that a checking must be done 6 months later. The improvement of MR examination offers a better detection of very small tumours (2-3 mm). The cost of a MRI is equivalent to the cost of 2 BERA. In conclusion, we propose MRI as the only investigation to be performed in case of an unilateral sensorineural hearing loss.