Technical Abstract: Buried seed reserves in soil (seed banks) are a major source of future plant emergence. Seed production from many annual weed species is high and the longevity of seed banks suggests existing mechanisms of seed protection. The role of microorganisms in seed fate is poorly described, as are seed bank factors influencing microbial growth, survival, or seed associations. In this study, we characterized microbial populations associated with seeds of weed species (velvetleaf, giant ragweed, Pennsylvania smartweed, jimsonweed, woolly cupgrass) as affected by exposure to soil inocula. With the exception of velvetleaf, seeds resisted decay during three months exposure to soil microorganisms. Terminal restriction fragment and rDNA sequence analysis indicated correlations between seed associated community structure and soil type. Within a soil, however, common taxa and closely related microbial species were present on replicate seeds, suggesting specific plant-microbe relationships. Few fungi and bacteria were detected microscopically or by PCR on surfaces of seeds collected directly from plants, but abundant growth and diversity of both fungi and bacteria were found on seeds incubated with soil-derived inocula. Major bacterial phylotypes found were Bacteroidetes and subclasses of Proteobacteria. Primary fungal phylotypes included members of Ascomycota and Basidiomycota. The results suggest seeds may provide a selective environment for microbial associations, and for certain weed species, the potential for seed decay by microorganisms is widespread but somehow limited in natural soil. This study investigates an aspect of the fundamental relationships between microorganisms and weed seeds, with broader implications for soil seed bank ecology in natural systems.