Introduction Over the past several years@ the United States has launched a major effort to assess the effects of acidic deposition on the terrestrial and aquatic components of the ecosystem. With the recent awareness that observed forest decline In Europe and Scandinavia may be associated with acidic deposition and/or other air pollutants (e.g.@ sulfur dioxide@ nitrogen dioxide@ and ozone)@ the United States Government has expanded its effort to characterize available air pollution data collected from monitoring sites In the United States and Europe where forest decline has been observed. Beginning in the early 1970s@ the occurrence of an unexplained foliar disease on European silver fir was noted in West Germany. Cowling (1984) has described some of the dominant characteristics of the generalized decline as follows: ? Symptoms of decline occur principally on fir@ spruce@ beech@ and pine@ but also on the hardwoods including birch@ larch@ maple@ alder@ ash@ and oaks; ? Both natural and planted forests are affected; ? Effects are seen at high and low elevation and on all aspects@ but are most pronounced on northwest-facing slopes in northwestern Germany and on west-facing slopes above 800 m in the Black Forest of Baden Wurtemburg in the southwest; ?While effects have generally been most pronounced on older trees@ they can be found on all age classes in many areas; ?Symptoms can be found on stands growing in soils of high or low fertility and on both basic and acid soils (pH range from below 3.5 to 8.0). Observations of increased mortality and widespread decline in the growth and behavior of softwood and hardwood forests of central Europe have led to speculation that air-borne chemicals may be among the causal factors (McLaughlin@ 1985). Besides the Federal Republic of Germany@ the mortality and growth-decline This study contains information@ developed from the site specific ozone and sulfur dioxide dose surrogates@ that has identified those national forests that may require further research. Because of the limited biological effects data base@ discretion has been urged in interpreting the information contained in the report. Focus in this report has been placed on identifying monitoring sites that experienced large frequencies of hourly episodic occurrences. However@ until further research is undertaken to ascertain the air pollutant levels@ their frequency of occurrence@ and time between episodic events that elicit permanent biological effects@ it will be difficult to objectively identify@ using ambient air quality information@ sites that may be at risk. A coordinated@ but independent@ effort is required to identify what 1) pollutant concentrations and 2) distribution patterns elicit vegetation effects.