Riffle beetles (Elmidae:Coleoptera) are popular biological indicators of unpolluted, well-aerated stream conditions.  However, we commonly find riffle beetles in streams in southeastern Ohio that are heavily impacted by acid, sulfur and metal loadings from abandoned coal mines. In laboratory assays, we demonstrated that adult Stenelmis, Macronychus and Dubiraphia are tolerant of acute acid exposures (pH=3.0 for 72 h) and respond with little or no mortality (< 5%).   In the field, riffle beetle abundances at over 40 sites declined with increasing acid mine impact, although beetles were sometimes found at sites with a pH as low as 4.4.  Dubiraphia sp. appear to be more tolerant of acidity and sulfates, whereas Ancyonxy sp. is the least tolerant.