The foliar nitrogen and phosphorus contents of 25 gallery forest trees on the Konza Prairie Research Natural Area were measured 1 month before and immediately after autumnal abscission in 1979. Leaves from five trees each of bur oak (Quercus macrocarpa), chinquapin oak (Q. muhlenbergii), green ash (Fraxinus pensylvanica), hackberry (Celtis occidentalis) and red elm (Ulmus rubra), ranging in diameter from 3-77 cm, were sampled. Total leaf contents varied from 47-219 micrograms nitrogen cm-2 and 4.3-23.8 micrograms phosphorus cm-2. Pre- to postabscission decreases of nitrogen and phosphorus were statisticaly significant in all species except red elm. Mean foliar nitrogen decreases varied from 13.2-54.2% among species and followed the order, chinquapin oak> bur oak> hackberry> green ash> red elm. Mean foliar phosphorus decreases varied from 7.9-36.7% and followed the order, buk oak> chinquapin oak> green ash> hackberry> red elm. Phosphorus reductions were much lower than reductions reported for other hardwood forests in the United States. This may be a function of the availability of soil phosphorus at the various sites. Tree age and diameter were positively correlated with the magnitude of nitrogen reductions. However, stepwise regression models based on all species combined indicated that age and diameter accounted for little of the variance in nitrogen decreases. The measured reductions in foliar nitrogen and phosphorus were not caused by leaching or insect herbivory, but rather were the result of biologically controlled nutrient resorption