Acid mine drainage (AMD) from abandoned coal mines in a 70-km² watershed in Western Pennsylvania has severely impacted stream ecosystems. Seven stations, 2 of which are unimpacted reference streams, have been sampled on 23 dates since 1996 to monitor changes in water chemistry and macroinvertebrates resulting from 16 reclamation projects involving passive treatment systems that remove approximately 190, 150 and 8 tons/y of acidity, Fe and Al, respectively. Trend analysis indicated a significant increase in pH and alkalinity at the lowest stream site in the watershed from 1996-2007. Soluble Cd and Ni significantly decreased, and there were no significant changes in Al, Fe and Mn. Macroinvertebrate density, richness and EPT values all significantly increased at this site as community composition changed from a fauna characterized by Hydropsychidae and Chironomidae to one containing more Ephemeroptera, Elmidae and Rhyacophila sp. However, macroinvertebrate densities at the lowest site (0-112 individuals/m²) are still approximately an order of magnitude less than in the reference streams, with richness (0-11) and EPT (0-5) values about half of those in reference streams. The limited biological recovery in this watershed probably results from continued poor substrate quality, and insufficient reduction in some potentially toxic metals.