Growth in the field of medical education is evidenced by the proliferation of units dedicated to advancing Medical Education Research and Innovation (MERI). While a review of the literature discovered narrative accounts of MERI unit development, we found no systematic examinations of the dimensions of and structures that facilitate the success of these units. We conducted qualitative interviews with the directors of 12 MERI units across Canada. Data were analyzed using qualitative description (Sandelowski in "Res Nurs Health" 23:334-340, 2000). Final analysis drew on Bourdieu's ("Outline of a theory of practice." Cambridge University Press, Cambridge, 1977; "Media, culture and society: a critical reader." Sage, London, 1986; "Language and symbolic power." Harvard University Press, Cambridge, 1991) concepts of "field," "habitus," and "capital", and more recent research investigating the "field" of MERI (Albert in "Acad Med" 79:948-954, 2004; Albert et al. in "Adv Health Sci Educ" 12:103-115, 2007). When asked about the metrics by which they define their success, directors cited: teaching, faculty mentoring, building collaborations, delivering conference presentations, winning grant funding, and disseminating publications. Analyzed using Bourdieu's concepts, these metrics are discussed as forms of capital that have been legitimized in the MERI field. All directors, with the exception of one, described success as being comprised of elements (capital) at both ends of the service-research spectrum (i.e., Albert's PP-PU structure). Our analysis highlights the forms of "habitus" (i.e., behaviors, attitudes, demeanors) directors use to negotiate, strategize and position the unit within their local context. These findings may assist institutions in developing a new--or reorganizing an existing--MERI unit. We posit that a better understanding of these complex social structures can help units become savvy participants in the MERI "field". With such insight, units can improve their academic output and their status in the MERI context-locally, nationally, and internationally.