This article draws on evidence from a small-scale study carried out in two early years classrooms. The study investigated an approach that appeared to enable very young children to construct and to write an argument. Multi-disciplinary theoretical perspectives are utilized for an explanation of the findings, with the work of Kress (1989) and Andrews (1995, 1997) on the nature of argument itself, Donaldson (1993) and Bereiter and Scardamalia (1993) on the value of writing to structure and develop thinking, being the most prominent. The case studies discussed here show that 5-7 year olds can engage with contentious, real-life issues and if offered structured support, they are able not only to produce written texts in the argument genre but their thinking also develops. A collaboration between professionals from different fields of education which aimed to support children's learning in literacy reaffirms the impressive competence of early years pupils.