Six reaches in each of two large rivers (one each in Kentucky and Ohio) were sampled using a prototype benthic macroinvertebrate sampling technique. The intent was to better understand the relationship between large river macroinvertebrate assemblages and habitat features. This information was to determine an acceptable sampling design to support development of a large river bioassessment protocol (LR-BP). Specific objectives included determining the appropriate number of habitat point-samples to be collected, examining how varying reach length affects assemblage characteristics, and determining an appropriate laboratory subsample size to accompany the resulting field sampling method.