Marilyn Field-Marsham practiced as a lawyer for over 20 years at Osler, Hoskin and Harcourt in Toronto, and has been involved in a wide variety of business issues and complex commercial cases. Several were landmark cases, involving national and multi-national corporations. She was a director of AIM Canada Fund Inc., AIM Global Fund Inc. and AIM Trimark Funds Advisory Board. She has served on the boards of several not-for-profit and public companies over the past 15 years and also on their governance, human resources, finance and audit and investment committees. She is the chair of the Mount Pleasant Group of Cemeteries in Toronto and the incoming chair of the governance committee of the Mount Pleasant Memorial Services. She is a governor of Opportunity International Canada. She acts as a volunteer, teaching governance to aboriginal communities in Ontario. She served as chair at the American Bar Association on the intellectual property and false advertising committees and on other advisory boards. She served on the editorial board and as contributing editor to the Intellectual Property Law Quarterly, Corporate Lawyer Series, Federated Press. She has had numerous speaking and teaching engagements at annual meetings of the Canadian and American Bar Associations, trade associations and professional development and continuing legal education seminars. She is also author of numerous articles on developments in legislation and jurisprudence. She has been actively involved with the Canada Blooms Horticultural Society, Massey College University of Toronto, Toronto Trees and Parks Foundation, and supported Trails Youth Initiative. She is currently a volunteer for the aboriginal governance and strategic planning projects, CESO (Canadian Executive Services Organization).