The threats posed by air pollution and climate change have resulted in considerable public debate about forest condition and growth during the past two decades. Despite the massive input ofresearch resources, no clear answers have been found to these global questions. Although there have been substantial advances in our knowledge of the effects of air pollutants on the forests, many of the questions associated with forest condition are still open. Monitoring of forest condition at the national level started in Finland in 1985 in accordance with the methodology drawn up by the International...