Previous studies have reported difficulties in analysing students’ argumentation. Especially the warrant, which connects data with claims, is found to be problematic to recognise. Weexamine how specific criteria for different forms of reasoning could decrease this difficulty. Instead of identifying warrants, we recognise whether students’ argumentation contains explicitly stated reasoning. We have developed an analysis method for recognising reasoning in argumentative talk. We collected video data from two mathematics lessons where students had to state claims about a mathematical situation and build convincing justification for their claims. The focus of analysis is in how the students articulated why the posed claim is true. Three cases illustrate how criteria for different forms of reasoning help in recognising whether the students articulate their reasoning.