From both a Bourdieusian and a new political sociology of science perspective, this research focuses on the relations of domination within the medical research field. The empirical case focuses on the disqualification of bronchial clerance in cases of bronchiolitis. The controversy involves actors with asymmetrical social positions, physiotherapists and paediatricians, and an institution supporting a process of expertise, the HAS. Oppositions are set up to try to legitimize contradictory scientific results, in a more general context of increasing Evidenced Based Practice. Despite these changes, in the end, medical academics reaffirm their domination of the biomedical research field and their claim to control the work of their auxiliaries.