Specific Language Impairment (SLI) occurs in 6.3% of children, twice as much in males than females. Deficits in phonology may include difficulties with early speech sound production, and/or weak phonological awareness skills, resulting in struggles with reading and writing. Chapter 1 reviews the most relevant research published that informs the definition, identification and treatment of expressive language impairment (ELI) in children ages 3 to 10 years old, with a focus on phonetic and phonological interventions. Chapter 2 explores the place of coarticulation in the phonology/phonetics dichotomy, relating coarticulating to what may in essence be viewed as its phonological counterpart - assimilation. Chapter 3 addresses how an approach based on phonological principles can be a reliable method for the speech intervention in children with cleft palate and compensatory articulation errors. A categorically stratified scale for classifying compensatory articulation errors according to severity and response to therapy is described. Finally, some strategies for speech intervention which are more suitable for a phonological and linguistic intervention are presented. The chapter explains how is that selecting the strategies to be used during the intervention according the severity of the articulation errors seem to increase their effectiveness.