The International Congress for Mathematics Education (ICME) is interested in teachers of mathematics and how they collaborate. By this we mean a deliberate and sustained initiative of collaboration, not just a chat over coffee. Collaboration could be organised to take place with colleagues in one or more schools, researches, business or other parties. We are looking at research on the topic but are also aware that a lot of valuable collaboration goes unreported. We're trying to develop an understanding of a) what's going on and b) what works well and c) why. We have studied the NCETM reports from the Collaborative Teacher Projects (well worth looking at!). We're asking this forum, and more widely, about the experiences of individual teachers of mathematics (at any level). Please comment to share your experiences, or, even better, complete the questionnaire here. We will share the results!