Demography spatial pattern and diversity of canopy and subcanopy trees shrubs and lianas were compared in two cool and two warm temperate North American forests paired at 30¬8 and 40¬8 north latitudes. All woody stems ge1 cm dbh in 16 randomly located non-contiguous plots totalling 1 ha at each of the four sites were measured mapped and identified. Basal area and overall density did not differ between latitudes. Demographic and spatial analyses revealed remarkable similarity in spatial dispersion irrespective of density or species composition. At all sites dispersion of canopy trees was random but all understory stems were uniformly distributed relative to all canopy trees. Species diversity and vertical structure differed between the warm and cool temperate sites especially in species composition of individual strata. Associations of understory species relative to canopy species were more random at 30¬8 than at 40¬8 north where a higher degree of association between canopy and understory species\ patterns coupled with their size class distributions suggested more lengthy regeneration cycles and an alternation of species assemblages. The forests at 30¬8 those subject to periodic canopy disturbance by hurricanes had more vertical mixing of species (i.e. canopy species represented in all size classes) more tree saplings and significantly more shrub and liana species.