This is the first in a series of papers intended as guides to the current and future directions of the Canadian Forest Service science program. It defines "forest health" and describes why the Service, in co-operation with a wide range of partners, addresses forest health issues through research, monitoring, and assessment activities in its science and technology research networks. Research areas are outlined in the fields of exotic insects and diseases, global environmental change, biological diversity, and forest management. Finally, some emerging issues in forest health are listed.