In studies of the northeastern red spruce ecosystem, several points evoke some agreement: (1) many high-elevation sites exhibit substantial post-1960 mortality that could be due to winter injury; (2) there is widespread pre-1950 growth increase with a subsequent post-1960 growth decrease; (3) many locations show none of these effects; and (4) dendro-climate models suggest that late summer and early winter temperatures of the previous year are significant determinants of red spruce year-to-year growth. It is a mistake to advocate a single cause at this time, because there is compelling evidence that both climate and stand dynamics are involved to some degree. The study of long-term forest trends based on tree-ring data is difficult and subject to interpretation, but it is unlikely that other data is available for most natural forest areas. In fact, progress made in the study of northeastern red spruce owes much to tree-ring analysis, and other ecological studies could benefit as well.