Published data on the total aboveground woody biomass (stems and branches), W T, of 640 forest and woodland stands around the world (Cannell, 1982) were divided into 32 species groups. Differences between groups were examined in the relationship: WT = F( HG) D, where F was a stand form factor; H was mean tree height; G was basal area at breast height; and D was mean wood basic specific gravity. W T was linearly related to ( HG); broadleaved species, owing to their greater D, had greater regression coefficients than conifers. Regression coefficients and F factors tended to be smallest in groups having the smallest percentage biomass as branches and greatest in those having most branches. F factors of about 0.5 corresponded to groups having 5–10% branches. The shapes of the woody parts of trees in those groups would conform most closely to quadratic paraboloids as hypothesized by Dawkins (1963) and Gray (1966). But heavily branched broadleaved stands had F factors of 0.6–0.8, and the F factor of tapped Hevea rubber with 81% branches exceeded 1. Thus, for any given G and H, the greatest W T was contained in those forests which had the greatest proportion of branches.