Purpose: To explore Canadian physiotherapists' perceptions of the factors that influence their decisions whether to supervise students in clinical placements. Methods: Using accepted survey development methodology, a survey was developed and administered to 18,110 physiotherapists to identify which factors contribute to the decision to supervise students. The survey also gave respondents opportunities to provide comments; these were analyzed via directed content analysis, using the factors identified in an exploratory factor analysis as an organizing structure. Results: A representative sample of 3,148 physiotherapists responded to the survey. Qualitative analysis of respondent comments provided a rich understanding of the factors contributing to the decision on whether to supervise students, which centred on themes related to stress, workplace productivity, the evaluation instrument, student preparation, and physiotherapists' professional roles and responsibilities. Challenges specific to loss of income and the ethics of charging for student services in private practice were also identified. Conclusions: Supervising students can be stressful, and stress is perceived by respondents to be most influential in deciding whether to supervise students. Effective supervisor training may mitigate some of the stresses related to supervising students. A collaborative approach involving all stakeholders is needed to resolve the issues of student placement capacity.