Within the field of bioethics and among many clinical trialists, the term “professional” has come to have a very specific meaning when referring to research participants. As highlighted by Roberto Abadie’s book The Professional Guinea Pig,2 the focus is largely on those participants, particularly healthy volunteers, who enroll in clinical trials as though it were their full-time job. In contrast, the excellent article by Zvonareva et al.3 illustrates that the term “professional” can be interpreted in multiple ways that differentially attend to who enrolls in clinical trials and how they perceive their role as research participants. Drawing upon the sociology of professions,4,5 Zvonareva et al. are particularly interested in the specialized knowledge and skills that healthy volunteers acquire through their clinical trial involvement, making them highly reliable—and thus valuable—participants. By learning what is expected of participants during Phase I clinical trials, healthy volunteers can dramatically support the workflow of trialists who must adhere to highly rigid procedure schedules, such as timed dosing of investigational drugs and blood collection. Zvonareva et al. demonstrate that when healthy volunteers adopt a positive work ethic toward their contribution to clinical trials, they engage in a type of identity work6 that allows them to see value in the contribution they are making to science beyond the financial compensation they receive. However, Zvonareva et al. also note that healthy volunteers are not formally credentialed or certified, so unlike traditional professions, they have limited power and no prestige conferred by their professionalizing activities.