Using two conceptual frameworks--boundary work and field theory--I examined how academic scientists' strategies for demarcating science from the market have implications for professional socialization. I focused on how field theory's emphasis on group differentiation, power, and rules within fields can inform analysis of boundary work. The study was organized around two questions: How do academic scientists demarcate the fields of science and the market? What role do noncommerical scientists, graduate students, and postdoctoral scientists play in commercially oriented scientists' boundary work? Drawing from in-depth interviews with 61 commercialist and traditionalist scientists at commercially intensive research universities, I identified three "rules" that operate as boundaries between science and the market. Commercialist adherence to these rules translated into a particular practice of third party impression management in which commercialists used postdoctoral scientists to segment science from the market. The liminality of postdoctoral scientists, which originates in their status as trainees between formal education and permanent positions, doubled as commercialist advisors situated them in the space between the fields of science and the market. The findings suggest that contemporary ways of protecting the integrity of the professoriate may operate at the expense of the long-term health of the profession by undermining professional socialization.