Removal of metals from mine drainage involves a host of chemical and biological processes including oxidation and hydrolysis rea ctions. The rate o f reactions is dependent on mine water pH, prese nce of bac terial cat alysts, and the availability of oxygen. Oxygen availability becomes particularly important in treatment systems using aerobic processes such as settl ing ponds and wetlands. Although oxygen is readily available in the atmosphere, encouraging the transfer of oxygen to mine water can be a challenge. Applicability of the various methods to increase oxygen levels in mine water is dependent on mine water chemistry and the availability of treatment area, hy draulic h ead, and power. I nnovative aer ation techniques have been developed which use wind, water, and electricity as power. The suitability of techniques must be evaluated on a site-by-site basis. Wind energy has been harnessed using windmill aeration techniques at t he Sagamore site in Fayette County, Pennsylvania. Water energy has been utilized through manipula- tion of available hydraulic head to improve aeration as demonstrated at the Kolb site in Indiana County, Pennsylvania. In cases where adequate aer ation cannot be accomplished by passive methods, such as the Kem pton site in G arrett Co unty, Maryland, active mechanical aeration using electric power may be a cost-effective alternative.