AbstractCallery pear (Pyrus calleryana Decne.), a native of eastern Asia, has recently emerged as an important woody invader in much of the eastern United States. Little is known about its ecology in its new range. Its shade tolerance may be an important indicator of areas it is likely to invade. In this study, allometric equations were first developed to predict aboveground biomass components, including wood, branches, bark, leaves, and fruit, from diameter at stump height (dsh; 25 cm), by destructively harvesting 13 trees, ranging from 0.1 to 19.3 cm dsh. Then, a total of 23 wild-grown stands in the northern Kentucky/southwestern Ohio region were surveyed, with diameters of all woody stems sampled. Pyrus calleryana density, basal area, aboveground biomass, stand density index, size distribution inequality, and importance value were calculated for each site. Two-factor Weibull distributions were fit to diameter distributions. Allometric equations provided good fits for total aboveground biomass as well as individual components. Aboveground biomass levels fell below mean levels of native forest stands found in the United States. Stand density indices yielded values typical of shade-intolerant or midtolerant species. Stands with smaller trees generally had steeply declining monotonic diameter distributions, while stands with larger trees trended toward positively skewed monotonic distributions. These findings are consistent with a species that is either shade-intolerant or midtolerant. Thus, while this species is expected to invade open or disturbed areas, it is not expected to be an important invader under forest canopies. However, its extended deciduous habit is one shared by other understory woody invaders, and so this may allow it to survive under forest canopies.