Due to the rapid technical development and increasing availability of diagnostic tests, the use of diagnostics by general practitioners and medical specialists is increasing. However, the excessive use of diagnostic tests is also explained by the behavior of the doctors as well as patients. In this Perspective we outline factors that perpetuate excessive use of diagnostic tests, further fuelling overdiagnosis. Solutions to achieve a sustainable culture of more sensible and cost effective diagnostics in both primary and secondary care will have to focus on a combination of factors, in which behavioral interventions for doctors and public information for citizens should play an important role. Worldwide movements such as Too Much Medicine, Choosing Wisely, but also the Dutch 'Doen of Laten' campaign can support this. It will take brave doctors, informed patients, and a supportive work culture.