Abstract: A promising low-technology solution for treating acidic mine drainage (AMD) emanating from coal mined lands involves the use of constructed wetlands.^The research was directed at addressing questions about retention mechanisms for the long-term storage of iron and manganese in constructed wetlands dominated by broad-leaved cattails (Typha latifolia).^Three sites in central Pennsylvania spanning the range of water chemistry parameters found in AMD were investigated.^When the AMD was circumneutral, and metal loadings were low, 79% of the iron, and 48% of the manganese were retained on average.^In the highly acidic site (pH approx.^= 3), < 10% of the metal loadings were retained.^The primary retention mechanism appears to be the formation of metal oxides in the aerobic zones of the sediments.^Although most microbial isolates extracted from sediment cores originated in the aerobic portions of the sediments, there was no evidence that they were transforming metals.^When AMD is circumneutral and metal loadings are low, constructed wetlands can be an effective approach to treating mine drainage.^At sites with highly acidic waters and high metal loadings, the use of constructed wetlands to treat AMD may be ineffectual, and should be implemented with caution.