One of the important roles graduate students play in University communities is that of graduate teaching assistant (GTA). As a result of the limited Canadian research on teaching assistants this research project explored the roles of GTAs and their training and support needs. The sample consisted of 234 GTAs representing Masters and PhD students from all departments at the University of Guelph. A survey instrument investigated GTA roles and responsibilities, self-perceptions of effectiveness, preferred training initiatives, and teaching experience variables. It was found that GTAs at this institution perceive themselves to be quite effective and are primarily responsible for grading, laboratory supervision, and 'support oriented activities'. Identified preferences for specific training and support content, included creating and conducting lectures, grading, and leading seminars. Department-based training and interactions with course instructors were highlighted as the preferred training formats. Implications for TA programming at the University of Guelph, and other institutions of higher education across Canada are discussed.