The aim of this research was to gain insight into the experiences and perspectives of individual members of a Medical Research Ethics Committee regarding their individual roles and possible tensions within and between these roles. We conducted a qualitative interview study among members of a large MREC, supplemented by a focus group meeting. Respondents distinguish five roles: protector, facilitator, educator, advisor and assessor. Central to the role of protector is securing valid informed consent and a proper risk-benefit analysis. The role of facilitator implies that respondents want to think along with and assist researchers in order to help medical science progress. As educators, the respondents want to raise ethical and methodological awareness of researchers. The role of advisor implies that respondents bring in their own expertise. The role of assessor points to contributing to the overall evaluation of the research proposal. Various tensions were identified within and between roles. Within the role of protector, a tension is experienced between paternalism and autonomy. Between the role of protector and facilitator tensions occur when the value of a study is questioned while risks and burdens for the subjects are negligible. Within the role of assessor, a tension is felt between the implicit nature of judgments and the need for more explicit formulations. Awareness of various roles and responsibilities may prevent one-sided views on MREC work, not only by members themselves, but also by researchers. Tensions within and between the roles require reflection by MREC members.