{Elevated atmospheric CO2 has the potential to influence rates of C and N cycling in terrestrial ecosystems by altering plant litter chemistry and slowing rates of organic matter decomposition. We tested the hypothesis that the chemistry of leaf litter produced at elevated CO2 would slow C and N transformations in soil. Soils were amended with Populus leaf litter produced under two levels of atmospheric CO2 (ambient and twice-ambient) and soil N availability (low and high). Kinetic parameters for microbial respiration and net N mineralizatino were determined on soil with and without litter during a 32-wk lab incubation. Product accumulation curves for CO2-C and inorganic N were fit to a first order rate equation using nonlinear regression analyses. Although CO2 treatment affected soluble sugar concentration in leaf litter (ambient = 120 g/kg