This paper examines the role of the sociocultural background of students for choosing STEM fields in university. We combine rich survey data on university graduates in Switzerland with municipality level information from the census as well as nationwide elections and referenda to characterize a student's home environment with respect to religious and political attitudes towards gender equality and science-related issues. Our empirical estimates are based on a structural Roy model which accounts for differences in costs (relative distance to the next technical university) and earnings across majors as well as for selection bias. Our findings suggest that male students from conservative municipalities are more likely to study a STEM field, whereas the sociocultural background plays little role for the major choice of females.