A phytosociological investigation was conducted in a virgin northern hardwood-spruce- fir forest in the lower elevations of the Bowl in the White Mountains of New Hampshire to determine the structure and dynamics of relatively small units of the forest. There is no evidence that the composition of the present forest has been influenced by human activity or fire, though portions of the present community demonstrate the effects of catastrophic damage caused by a severe hurricane in 1815. Forty-five 20- by 30-m plots ranging in elevation from 586 to 920 m were studied. Tree densities ranged from 685 to 3,851 stems/ha, basal areas from 22.0 to 60.5 m21ha, and shrub-seedling densities from 0.15 x 105 to 2.27 x 105 stems/ha. Bray and Curtis ordination was used to position the plots on the X and Y axes of a vegetational mosaic. The primary differentiating species were Picea rubens and Acer saccharum on the X axis and Betula alleghaniensis and Fagus grandifolia on the Y axis. The ordination was divided into seven subjectively defined plot clusters based primarily on the size-class distributions of four major tree species found in each plot. Cluster A represents a high-elevation, stable Picea abies unit. Cluster B represents a lower elevation, edaphically controlled Picea-Abies-Fagus grandifolia- Betula alleghaniensis unit which is projected to develop into a Picea-Abies-Fagus grandifolia unit. Clusters C to G represent stages in a successional sequence initiated by a catastrophic blowdown. The sequence is postulated to start with a Betula alleghaniansis Reproduction-Sapling unit, none of which was observed in the present forests of the Bowl. This stage develops into an All-Sized Immature Betula alleghaniensis unit (Cluster C) followed by a Mature Betula alleghaniensis/Sapling Acer saccharum-Fagus grandifolia unit (Cluster D). Then, depending on tree density, will follow a Mature Fagus grandifolia/Residual Decadent Betula alleghaniensis unit (Cluster E) or a Mixed Acer saccharum-Fagus grandifolia/Residual Decadent Betula alleghaniensis unit (Cluster F). Cluster F develops into a Decadent Acer saccharum-Fagus grandifolia unit (Cluster G). This and the unit represented by Cluster E could develop into a Hypothetical Decadent Fagus grandifolia/Acer saccharurn unit.