During preparation for professional practice, the professional skill being developed is typically measured in the form of specific knowledge and skills. This study proposes an alternative to such measures, drawing upon research which demonstrates that our understanding of professional practice is central to how we both perform and develop that practice. The study investigates understanding of medical practice prior to and following a pre-medical programme. On commencing the programme, students showed substantial variation in their understanding of medical practice. At the end of the programme much of this variation remained, indicating the students had developed varying forms of professional skill. The study calls into question the adequacy of a focus on detailed knowledge and skills as a base for professional practice. In line with previous research, an important implication of the study is that developing skilful practice requires focusing on understanding of that practice in and through its performance.