Objective: to study the pure tone threshold of patients after cochlear implant (CI) at National ENT hospital. Method: the cross section study evaluated the hearing threshold of 30 CI recipients from 9/2012 to 4/2014 at National ENT Hospital who were the children having pre-language bilateral severe to profound hearing loss. Results: pure tone hearing test were carried out to assess the Pure Tone Average (PTA) of 3 frequencies 500, 1000, 2000Hz before the operation and Pure Tone Average (PTA2) of 4 frequencies 500, 1000, 2000, 4000Hz post operation. Pre-operative PT A showed that 28 patients had bilateral profound hearing loss
only 2 patients had severe hearing loss in one ear and profound hearing loss in other ear. Post- operative showed that 100 percent PTA2 in the ear of CI was inferior 4sdB in which PTA2 from 2sdB to 3sdB occupied 70,1 percent. Conclusion: a helps the children with severe to profound hearing loss to recover the hearing level near the normal children so that help them learn hearing and speaking.