This paper describes the implementation and evaluation of the HARP system, a PC-based visual speech training aid for hearing-impaired people. The system offers teaching modules for a range of speech parameters, including intonation, rhythm, vowel quality and consonant production, and provides evaluative and diagnostic feedback to users. The development of the system is being assisted by consultation with hearing-impaired groups and speech and hearing therapists, and initial evaluations of a prototype aid have been completed.