Repeat photography and tree ring analyses were used to investigate structural change, 1938-88, of an old growth and high elevation Picea abies (L.) Karst. forest in northern Sweden. The forest, initially moribund, senescent and top-broken, regenerated broken tops and apparently gained in vigour. Up to the 1930s this progressive change was pre-dated by an increase of annual increment growth, which subsequently declined until the 1980s. The tree-ring response concurs with the general course of summer temperature while canopy processes appear to lag behind. The study stresses the importance of phenotypic plasticity for long-term behaviour of marginal spruce forest. It is also evident that canopy development is not a fully predictable ageing process, but to some extent dependent on climatic variability.