Widespread usage and detection of agricultural chemicals in surface and ground water systems has prompted many researchers to monitor their fate in the environment. Despite the potentially important role of microorganisms in the biodegradation process, microbial responses to agricultural chemicals are largely unknown. Our investigations were an effort to determine the innate ability of surface soils and subsurface sediments to attenuate agricultural chemicals prior to chemical migration into aquifers. The objectives of our studies were to investigate microbial degradation potential of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D} and to determine baseline microbial populations and activities in surface and shallow subsurface sediments from two Midwestern agricultural watersheds. The size and diversity of microbial populations were investigated in soils and down into subsurface glacial till and alluvial sediments. The microbial, physical, and chemical characteristics were monitored to determine if any variables could be used as indicators in predicting herbicide biodegradation.