목적: In cochlear implantation (CI), 3 to 8 % of cases require revision surgeries. Device failure after CI in one of the most common cause of reimplantation, reporting 4.8% including hard and soft failure. We aimed to introduce our experience of device failure after CI. 방법:We retrospectively reviewed the patient who underwent revision surgery after CI due to device failure from January 2000 to August 2021. Etiology of hearing loss, age on 1st and revision CI surgeries, operation information including surgical time, approach, electrical outcomes just after implantation, device, symptoms of device failure, history of head trauma, and audiologic outcomes with CAP score were investigated. 결과:From January 2000 to August 2021, 1941 cases of cochlear implantation were performed, and 35cases (1.80%) underwent revision surgeries due to device failure. One of the most and second most common etiology of CI were idiopathic (14/36) and cochlear hypoplasia (8/36). The mean age on 1st implantation was 11.4-year-old: patients of 26 pre-lingual and 9 post-lingual. Time from 1st implantation to revision surgery due to device failure was 43.0 months. Four different devices were used for CI during this period: Cochlear (77.7%), MED-EL (19.5%), Advanced Bionics (2.6%), and Oticon (0.2%). 9.8% of device failure was occurred in Advance Bionics, whereas Cochlear, MED-EL, Oticon demonstrated 1.06%, 3.70%, and 0%, respectively. The most common symptom that patients’ complaint was intermittency of sound. One year after 1st implantation, mean CAP score was 4.63, and 1 year and 3year after revision were 5.25 and 6.26, respectively. 결론:The most common symptom of device failure was intermittency of sound. If this symptom occur, device failure should be considered and need to perform electrical examination. Audiologic outcome demonstrated slightly improved after revision surgery. Following the time period, audiologic outcome has been improved after implantation over time, even revision surgeries were performed.