Recent research has shown that phosphate materials can ameliorate acid mine drainage (AMD) by immobilizing iron and inhibiting the production of acid by oxidation of fes2. A simulated weathering study was done to evaluate several regional phosphate resources, followed by application rate determination using a soxhlet leaching technique. Phosphate sources tested included two apatite ores (cominco ore and Texas gulf ore) at an application rate of 3 pct by weight apatite and two phosphate industry wastes (cominco waste and stauffer sludge) at application rates of 1, 3, and 5 pct apatite by weight. Leachate analyses indicated that all sources at all application rates resulted in significant decreases in titratable acidity versus a control. Texas gulf ore showed the greatest effect, with a 67 pct decrease. Iron concentrations in the leachate also were reduced, with stauffer sludge (5 pct) and Texas gulf ore producing the largest diminutions, 62 and 63 pct, respectively. Decreases in iron and in acidity levels appear to be primarily due to precipitation by po4 of iron derived from dissolution of pyrite oxidation products and not necessarily to a decrease in pyrite oxidation. Maximum decreases in so4 2- concentrations of 26, 20 and 25 pct were achieved by applications of Texas gulf ore and stauffer sludge (3 and 5 pct), respectively. The high effectiveness of Texas gulf ore and stauffer sludge is attributed to their high relative surface areas and p solubilities.