There are some children with speech and/or language difficulties who are significantly more difficult to understand in connected speech than in single words. The study reported here explores the between-word behaviours of three such children, aged 11;8, 12;2 and 12;10. It focuses on whether these patterns could be accounted for by lenition, as suggested by a usage-based approach to phonology. The children carried out a repetition task, with sentences containing environments that can trigger assimilation and elision. Speech elicited was examined using a combination of perceptual and electropalatographic (EPG) analysis. All of the children produced instances of word boundary behaviours reported in adult speech, as well as some which are considered to be atypical. It is argued that all of these phenomena can be viewed as lenition, and that a usage-based approach to phonology has potential for providing a valuable framework for the description of between-word processes in disordered speech. (Contains 9 figures and 2 tables.)