Speech perception outcomes for people with a prelingual hearing loss, implanted with a cochlear implant in adolescence or adulthood, are characterized by a large degree of variability. Research findings indicate that some recipients do very well and gain significant open set speech perception skills, whilst a large percentage show little or no change in open set speech results, post implant. In studies to-date, mean speech perception scores were typically substantially poorer than those recorded for implant recipients with a postlingual hearing loss. Despite this, the majority of recipients with a prelingual hearing loss implanted with a cochlear implant in adolescence or adulthood reported satisfaction with their implant and used it regularly. Although there have been a number of studies in the area, none has taken a holistic approach and investigated both objective and subjective outcomes for a large group of participants. In addition, no study has employed a multiple regression analysis to investigate which characteristics were associated with speech perception outcomes in people with a prelingual hearing loss implanted with a cochlear implant in adolescence or adulthood. The objectives of the study were to examine speech perception and other outcomes in people with a bilateral prelingual or perilingual hearing loss, implanted with a cochlear implant as an adolescent or adult, and to investigate prognostic factors associated with positive outcomes. The design consisted of a retrospective review of both speech perception outcomes and other outcomes for 38 recipients, diagnosed with a bilateral hearing loss before age 3, and implanted with a cochlear implant at 14 years or older. There were 24 females and 14 males and the average age at initial stimulation was 33 years. All participants were implanted with a Nucleus device at a private audiology clinic (Attune). Four questionnaires were completed by approximately half of the participants – Glasgow Benefit Inventory (GBI); International Outcome Inventory (IOI-CI); Study Questionnaire; and the Hearing Abilities and Quality of Life Scale. The Study Questionnaire was developed specifically for this project and investigated satisfaction, benefit and advantages/disadvantages of the implant. The Hearing Abilities and Quality of Life Scale was developed by Attune and was completed by recipients pre and post implant. It evaluated the ability to understand conversation in different situations, environmental awareness, safety concerns, involvement in social activities and impact of the hearing loss on relationships. Approximately one third of participants scored between 30 and 90% on the CID/ CUNY test administered via CD post implant and approximately one fifth scored over 90%. The mean score on the CID/CUNY test administered via CD was 8% pre implant and 48% post implant. Over 80% of recipients used their device more than 8 hours a day and all recipients reported being satisfied with it. Three factors accounted for 65% of the variance on the open set sentence test score, post implant. These were stable versus progressive loss, mode of communication in childhood and time without a hearing aid on the implant ear. For the purposes of this research, a ‘stable’ loss was defined as a bilateral severe to profound hearing loss at diagnosis and a ‘progressive’ loss was one that deteriorated to this degree at some point after diagnosis. The findings from this study reveal that a cochlear implant is a viable option for adults and adolescents with a prelingual hearing loss. The majority of participants gained benefit from the device and were satisfied with it. In addition, a substantial number gained good open set speech perception ability, post implant. Consistent with previous studies, there was large intersubject variability in speech scores. The recipients who had a progressive loss, used oral communication in childhood and wore a hearing aid on the implant ear up to the time of surgery were more likely to obtain better speech perception outcomes.