The objective of this experiment was to determine the amount of litter C incorporated into soil aggregate fractions under two tillage regimes in dryland agriculture. Mixtures of uniformly ¹³C-labeled (δ¹³C ‰ = 797.55) wheat residues were incorporated into incubation cores containing soil (δ¹³C ‰ = -17.71) under no-till (NT) and simulated conventional tillage (CT) at the dryland agricultural experiment in Sterling, CO. Samples were collected initially and after a one year incubation to estimate stabilization rates of residue-derived C in physically defined C pools. This labeling study compared NT and CT treatments and provided valuable information on how soil disturbance influences litter C into soil aggregates. Under both tillage systems, ¹³C-labelled wheat residue was incorporated into aggregate fractions in the following order: coarse particulate organic matter (>250μm) > macroaggregates (>250μm) > microaggregates (>53μm) > silt + clay (<53μm) > microaggregates-within-macroaggregates > silt + clay-within-macroaggregates. As expected, residue incorporation was greatest in the 0-5cm layer under NT and distributed throughout the three depth layers (0-5cm, 5-15cm, 15-30cm) under CT.