Speech and language therapy is a relatively new discipline. The profession was born some 50 years ago, uniting those working with mostly head injured soldiers returning from the second world war. Interest in communication at that time was lead by neurologists, ear, nose, and throat surgeons, and many teachers. As in many other disciplines, the foundations of the profession were based on concern for those with the disorders and an empirical approach to remediation.

We undertook a literature review to establish the state of knowledge about the efficacy of speech and language therapy in major client groups and to identify important areas for research.1 Not surprisingly, in view of the profession's youth, research has dealt more with the analysis and identification of speech and language disorders and the development of hypotheses underlying therapeutic programmes than with evaluating their efficacy, relevance, and validity.

We wanted to take a systematic approach to reviewing the research,2 but there are not enough controlled studies for us to confine ourselves to this approach. We therefore extended our review to studies displaying the state of knowledge and the main therapeutic challenges.

This review attempted to cover a broad range of published and grey literature and hence required interrogation of many different databases because the literature related to speech and language therapy appears in journals covering linguistics, psychology, social sciences, and education. Other reviews examining the efficacy of speech and language therapy have not reflected the wealth of literature because they have limited the search to Medline and associated medical databases.3 The main findings of the review are summarised in the box.