The Bercow Report (Bercow, 2008) commissioned by the UK government provided a high status impetus to improve services for children and young people with the full range of speech, language and communication needs (SLCN). A research study commissioned to provide evidence to Bercow (2008) identified both limitations and potential benefits regarding the collection, analysis and use of data on children and young people with SLCN. This article draws on that study of six local authorities and their partner primary care trusts, and on analyses of national statistics. The term "speech, language and communication needs" (SLCN) is shown to be used in England for two different populations: all children with some form of SLCN, whatever the cause, and the more specific group comprising children and young people with primary language difficulties. The article focuses mainly on the latter group and those with autistic spectrum disorder to explore the use of data available on children and the use of these data to aid collaborative planning by education and speech therapy services. It is concluded that local authorities are "data rich" with child level information, but effective use of these data for children with SLCN is limited. Collaborative data collection, analysis and use for policy or individual child level action by education and speech and language therapy services are even less common. Data are necessary to support the evaluation of interventions and provide an appropriate accountability framework. It is argued that effective data use by local authorities and primary care trusts, especially if working collaboratively, has the potential to improve services for children with SLCN. (Contains 4 tables and 3 figures.)