Objectives: To identify factors preimplantation associated with postimplantation speech perception improvement in the adult congenitally deaf population., Design: Forty-four adult cochlear implant (CI) patients who had a severe to profound hearing loss from birth were identified from this centre's database. Eight preimplantation factors, speech intelligibility, preimplantation hearing levels, communication mode, preimplantation speech perception scores, progression of hearing loss, age at implantation, hearing aid use preimplantation, and gender, were recorded during the CI assessment process. These factors were investigated to determine their effect on speech perception improvement postimplantation. The outcome measures were the improvement in scores for the BKB Sentence test and CUNY Sentence test with lipreading after implantation. In the final analysis, 26 patients were included in the CUNY analysis, and 30 patients were included in the BKB analysis., Results: Speech intelligibility rating, preimplantation hearing levels, and communication mode were shown to be significantly associated with improvements in speech perception postimplantation., Conclusion: Three factors were identified that affected speech perception improvement postimplantation: speech intelligibility, preimplantation hearing levels, and communication mode. These factors can be used to counsel CI patients regarding potential speech perception improvements from cochlear implantation, although these are based on average data and may not reflect individual performance.