Building relationships between universities and industry bodies is of prime importance for creating value for universities' stakeholders. This paper focuses on relationships in relation to undergraduate internship programmes in the Social Sciences. Using the relationship marketing approach, we analyze this type of collaboration of firms with a large public Spanish University. We build and test a structural equations model whose results show that communication is a key building block of relationships, having a positive effect on satisfaction with the relationship, trust and functionality of conflict, and that trust and commitment increase the level of collaboration of firms with universities.