This paper reports a study conducted in a laboratory classroom with the capability to record classroom social interactions in great detail using advanced video technology. The social interactions of student groups during collaborative problem solving were analysed based on transcript data. This analysis suggests that meaning negotiation in mathematics classrooms can be usefully distinguished as social, sociomathematical, or mathematical. We suggest that all three modes coexist in an entangled form in the negotiative interactions documented in the mathematics classroom and we envisage all three as constitutive of learning.