This paper reports on a clinical trial evaluating outcomes of a frequency-lowering technique for adolescents and young adults with severe to profound hearing impairment. Outcomes were defined by changes in aided thresholds, speech perception, and acceptance. The participants comprised seven young people aged between 13 and 25 years. They were divided into two groups based on their audiometric configuration. The first group consisted of four young people with pure tone thresholds of less than or equal to 100 dB at 1 kHz. The second group had more profound hearing loss, with pure tone thresholds of greater than 100 dB at 1 kHz. All participants attended the Fundacio Widex Audiologia in Barcelona, a charitable foundation offering intervention and habilitation programmes for hearing-impaired children of all ages. The participants were oral communicators integrated into mainstream high schools and universities. All were experienced hearing aid users with excellent spoken language and no other disability. The hearing aids were fitted using standardized procedures and were worn with the frequency transposition algorithm in the first programme for consistent everyday use. Phoneme and word recognition were assessed after 4, 8, and 12 weeks of use and compared with results for their own superpower hearing aids. Subjective comments from both the participants and their parents were recorded throughout the study. Notable improvements were observed in both sound-field-aided thresholds and speech perception after 12 weeks of use, suggesting that frequency lowering can be efficacious in improving speech perception in severely to profoundly hearing-impaired individuals who are past the critical age for language acquisition. (Contains 2 tables and 6 figures.)