One of the most important issue for selecting and fitting of hearing aids that should receive special attention is binaural amplification.According to several investigations, superiority of binaural amplification on monaural one is confirmed.Binaural Amplification may have considerable effects on fromation and developing of superior dimensions of hearing including: Localization, Binaural squelch (Better hearing in presence of noise).So, it is necessary to know the basic and scientific concepts and applicable principles of binaural hearing and binaural fitting.Present paper deals with this important subject.