This paper explores the concept and practice of interaction within a blended problem-based learning (PBL) module for academic professional development in higher education. A qualitative study spanning two years of the lived experiences of 17 academic staff in a blended PBL module was considered likely to provide a much-needed analysis of current thinking and practice on the potential of interaction. Relevant constructivist theories are applied to face-to-face PBL tutorials, online discussions, focus group interviews and reflective papers. For designers and tutors in blended PBL, it is important to seek best practices for how to combine instructional strategies in classroom and computer-mediated environments that take advantage of the strengths of each and avoid their weaknesses. Specific aspects of interaction (peer, tutor and the blended PBL learning experience) within face-to-face and online PBL tutorials are analysed to provide research-based information about the realities of delivering a PBL programme using a variety of current learning technologies. (Contains 2 tables.)