In this discussion paper, Suzanne Mackenzie, senior lecturer with responsibility for the special educational needs BA and MA programmes at the University of East London, reviews previous research in order to identify changes in the role of the special educational needs co-ordinator (SENCo) in schools in the UK. She provides an overview of the SENCo role from an historical perspective and discusses the diverse and challenging nature of the SENCo's work. She notes a marked lack of consistency, over time and across contexts, in interpretations of the SENCo role and examines variation in workload, status and position within school hierarchies. Suzanne Mackenzie highlights the gaps in current research on the work of SENCos and makes suggestions for future developments in the role. She focuses, in particular, on the ways in which SENCo "effectiveness" can be determined.