This paper reports some results from a case-study on five Swedish upper secondary school teachers' views of proof. We describe the teachers' views of what constitutes proof and focus particularly on their views on the role and relevance of proof in teaching mathematics. We identified two basically different ways of relating to the teaching of proof in our data that consists of interview transcripts and protocols of observations of lessons. We discuss these views from a socio-cultural perspective on learning and Wenger's concepts of community of practice, reification and participation.