Augmentative and alternative communication (AAC) is the collective term for a broad range of techniques, strategies and devices which can support children with communication difficulties who may have little or no intelligible speech. This may include manual signs or systems of symbols, words or letters that can be used to construct messages and convey meaning. This review discusses the ways in which AAC systems are categorized and outlines some key principles of assessment and intervention, using the World Health Organization's International Classification of Functioning, Disability and Health for Children and Young People as a proposed framework to guide decision-making. The review is aimed at healthcare professionals working with children...