Tillage may influence the microbial populations involved in soil aggregation.We evaluated the effects of no till (NT) and conventional tillage (CT, tillage depth about 7 cm) continuous spring wheat system on culturable heterotrophic bacterial communities predominant in microaggregates (0.25e0.05 mm) and on soil-aggregating basidiomycete fungi in aggregate-size classes (4.75e2.00, 2.00e0.25, and 0.25e0.05 mm) at 0e20 cm depth of a Williams loam (fine-loamy, mixed, Typic Argiustolls) in dryland Montana, USA. Enzyme-linked immunosorbent assay used to quantify antigenic response to basidiomycete cellwalls,was higher in NT than in CT in 4.75e2.00 mm size class in 2007 and higher in all classes and years at 0e5 cm depth, but was not different between tillage, years, and classes at 5e20 cm. The culturable bacteria from microaggregates were subjected to a soil sedimentation assay to determine their soil binding capability. The proportion of isolates which can function as soil aggregatorswas higher in NT than in CT at 0e5 cm but was not different at 5e20 cm. Our results provide a first insight into the beneficial effects of dryland NT compared to CT in reducing soil disturbance and residue incorporation and enriching the proportion of microorganisms responsible for aggregation, especially at the soil surface.