The article focuses on study visits from the perspective of mathematical project work. Project work means a systematic organizing method of teaching that is based around a project. The research questions are the kinds of study visits students made, the meaning(s) of those visits, the mathematical content in the visits and how such study visits should be developed. The research material consists of two questionnaires (one for teachers and one for companies) and a case study of a student group that carried out two study visits as part of their mathematical project work. The results show that both teachers and companies considered study visits to be significant from their own standpoints. The teachers organize study visits, but the content of the visits is not usually connected with activities in the classroom.