The article describes mathematicians' pedagogical perspectives on proof in the teaching of first year university students at a mathematics department in Sweden. A conceptual frame that was used in the data analysis combines theories about proof from earlier mathematics education research with a social practice approach of Lave and Wenger. A theoretical idealised model of three different teacher styles was constructed from the data that consist of transcripts of interviews with 13 mathematicians at the department. The model gives structure to the results and can be applied and developed when comparing teaching cultures between different departments in a country as well as between different countries. (Contains 1 table and 1 figure.)