This article analyses the ways in which research coordinators forge professional identities in the highly gendered organizational context of the clinic. Drawing upon qualitative research on the organization of the clinical trials industry (that is, the private sector, for profit auxiliary companies that support pharmaceutical drug studies), this article explores the relationships between predominantly male physician-investigators and female research coordinators and the constitution of medical expertise in pharmaceutical drug development. One finding is that coordinators actively seek to establish relationships with investigators that mirror traditional doctor-nurse relationships, in which the feminized role is subordinated and devalued. Another finding is that the coordinators do, in fact, have profound research expertise that is frequently greater than that of the investigators. The coordinators develop expertise on pharmaceutical products and diseases through their observations of the patterns that occur in patient-participants’ responses to investigational drugs. The article argues, however, that the nature of the relationships between coordinators and investigators renders invisible the coordinators’ expertise. In this context, gender acts as a persistent social structure shaping both coordinators’ and investigators’ perceptions of who can be recognized as having authority and power in the workplace.