We assessed the effect of benthic macroinvertebrates on leaf litter breakdown and associated microbial communities in a small coastal plains stream in western Georgia, USA, by quantifying litter breakdown and bacterial succession on single- and mixed-species leaf packs of red maple and water oak in the presence (control) and absence (exclusion) of macroinvertebrates. Exclusion of macroinvertebrates was accomplished by using fine-mesh (1-mm) litter bags, whereas we used coarser-mesh (6.35-mm) for controls; bags were incubated for 128 d. Litter was analyzed for bacterial diversity by automated ribosomal intergenic spacer analysis (ARISA), using the ITS region between 16S and 23S for bacterial genes, and breakdown was determined by ash-free dry mass (AFDM). Preliminary data indicated that exclusion treatments effectively reduced macroinvertebrate biomass, particularly for large shredders and scrapers. AFDM declined over the study but was higher for exclusion than control treatments (e.g., AFDM remaining for red maple in control vs. exclusion packs at 128 d was 46 vs. 69%, respectively). Bacterial taxa appeared as contrasting bands on ARISA gels; early results indicated bacterial succession over the study, the magnitude of which appeared to vary by treatment. Our data suggest that this method is useful in discerning macroinvertebrate-induced differences in litter microbial communities.