There has been a resurgence in applying bioassessment techniques for evaluating and monitoring the biological integrity of stream ecosystems. In all uses biological metrics have been refined to account for regional variation in aquatic habitats and fauna. This study evaluated environmental and macroinvertebrate properties for wadable streams in 3 major ecoregions Idaho: Northern Basin and Range, Snake River Plain. and. Northern Rocky Mountain. These 3 ecoregions constitute >80% of the land area in Idaho. Reference streams were delineated from test streams in each ecoregion using standard habitat assessment protocols (Plafkin et al. 1989). Multiple discriminant analysis effectively determined habitat (quantified measures) and macroinvertebrate differences between reference and test streams within ecoregions, although the results suggested that quantifiable habitat measures (e.g., water chemistry and nutrients) and biotic metrics based on taxonomic groups (e.g., % Elmidae) improved the discriminatory power of evaluation procedures. Our results support the contention of a multi-metric approach for assessing differences among streams within an ecoregion. Lastly, individual metrics differed in their importance or evaluating stream condition among ecoregions, further emphasizing the importance of regionally stratifying metric selection or scoring procedures.