Although bioassessment and monitoring activities on non-wadeable streams in the U.S. are occurring more frequently, methods for these systems are not as well developed as they are for wadeable streams. This issue was recognized by U.S. Environmental Protection Agency (EPA) regional scientists as being detrimental to their monitoring and enforcement activities and, through the Office of Science Policy's Regional Methods program, funding for a research initiative was awarded to the National Exposure Research Laboratory in Cincinnati, Ohio. This funding was provided to support the investigation of existing bioassessment and monitoring methods on nonwadeable rivers and the development of new methods where needed. We compared six benthic macroinvertebrate field sampling methods for nonwadeable rivers, two each adapted from those used by three major bioassessment programs. These programs are the U.S. EPA's Environmental Monitoring and Assessment Program for Surface Waters (EMAP-SW), the U.S. Geological Survey's (USGS) National Water Quality Assessment Program (NAWQA), and the Ohio EPA's Division of Surface Water Biocriteria Program. We performed all six methods at a total of sixty sites across four tributaries to the Ohio River. The equipment used, the mesh sizes of the equipment, and the key characteristics of the sampling technique varied greatly among these methods, ranging from qualitative to quantitative, from passive to active, and from subjective to systematic. In addition to macroinvertebrate samples, water chemistry and physical habitat data were collected at each site to assess relationships between macroinvertebrate metrics and abiotic site condition. A single protocol was used to collect water chemistry samples and the EMAP-SW protocol was used to collect habitat data. Sites were divided into two classes based on flow regimes. These classes included those sites influenced by navigational lock-and-dam structures built to support commercial traffic (i.e.,
restricted flow, or RF) and those sites that were free-flowing or had only low-head dams (i.e., run-of-the-river, or ROR).