Background: Electropalatography (EPG) is an instrumental technique which has been used to treat persistent speech sound disorders in school-aged children and adults born with cleft palate+/- lip. The effectiveness of EPG therapy with this client group has been reported in multiple case studies and small group studies (e.g. Gibbon et al., 2001). Findings show many individuals can change their speech with EPG therapy. However, patients commonly have difficulty with generalisation and maintenance of improvements following therapy, leading to the conclusion that further development of the EPG treatment technique is needed. This thesis describes and evaluates patients' response to a novel EPG therapeutic technique which uses usage-based phonological theory as its theoretical underpinning. In comparison to other phonological theories, which provide economical descriptions of sound systems, usage-based phonology presents an explanatory account of speech sound development (e.g. Menn et al, 2013). The resultant therapy technique focuses on high volume production of words and connected speech. Method: Six consecutively treated school-aged children and adults with long-standing lingual speech errors secondary to cleft palate enrolled on a multiple baseline (ABA) withinparticipant case series. Speech was assessed on three baselines prior to intervention, during weekly intervention at a regional hospital, at completion of therapy, and then 3- months post-therapy. Two speech and language therapists unrelated to treatment blindly transcribed and rated participants' speech. Results: Large treatment effect sizes were shown for all participants. Percentage of targets correct for treated and untreated words improved from near 0% pre-therapy, to near 100% post-therapy, for most target speech sounds. Generalisation of target sounds to spontaneous connected speech occurred for all participants and ranged from 78.95 - 100% (mean = 90.66) on maintenance assessment, 3-months post-therapy. Conclusions: Clinically relevant speech change occurred for all participants following intervention. EPG feedback was central for acquisition of speech sounds, while other aspects of the treatment approach appeared important for functional generalisation. EPG provided objective speech data and was an important complement to acoustic phonetic transcription. This therapy technique shows promise and further research is indicated.