if humankind is to cope with the cumulative effects of its expanding populations on the earth’s ecosystems, a new relationship is required with natural systems. serious adoption of the concepts of forest sustainability and adaptive management of forest ecosystems has meant a shift from a commodity focus in forest management to a focus on maintenance of ecosystems. a key step within an adaptive management framework is to identify indicators of essential ecosystem features. forest managers thus need to identify and apply indicators that can show whether forest sustainability is being achieved. the working definition of forest sustainability developed and incorporated in this project is that a forest, to be sustainable, will retain its essential ecological composition, functions, and patterns, which support the full range of societal values, in both the present and the long-range future. indicators were determined by developing measures for ecosystem features critical to ecosystem function and that satisfy a broad range of public values. public involvement in this process included circulation of a preliminary suite of indicators, and a workshop to prioritize indicators for development. economic values were not directly considered in the study. indicator development and application are embedded in the principles of landscape ecology, necessary for the implementation of an ecosystem management philosophy. a first-approximation set of indicators designed for application to the managed boreal forests of northern ontario is presented, as well as a test application of the indicators to a boreal forest near thunder bay. indicators identified and tested in relation to wilderness are remoteness, size of wilderness, and naturalness. indicators presented in relation to biodiversity are: forest cover type diversity, forest age diversify, forest fragmentation, old growth forest and old growth interior forest fragmentation, forest edge length, and habitat supply for specific species - marten. finally, road-related indicators identified and tested are road density, and forest conversion by roads and landings. recommendations for operational use of sustainability indicators in forest planning include the following. the public must be involved in the choice and formulation of indicators. existing digital fri databases, although problematic in some respects, can be an adequate starting point for indicator measurement. as a key component of managing for forest sustainability, indicator measurement will require additional personnel and effort. although indicator development and use will require more effort and money, development of at least a few indicaors for each forest management unit in ontario should begin immediately. indicator development is hampered by serious deficiencies in biophysical and socio-economic understanding of boreal forests. indicators must be tested on a range of forecasts for the future structure of forests, under alternative management strategies. since forest sustainability has become the first priority for forest managers, they will have to demonstrate to the public their success in the achievement of forest sustainability.