Poultry litter (PL) has useful nutrients and is therefore used as manure. In addition to N, P and K, PL also contains some heavy metals (As, Cd, Cu, Mn, Pb and Zn), antibiotics, antioxidants, mold inhibitors and other organic compounds. Poultry litter aqueous leachate (PLL) has been shown to be toxic to many organisms; PLL is more toxic than the aqueous leachate of other animal manures used on agricultural soils. Clayey soils are known to retain toxic heavy metals. The objective of this study was to measure the change in toxicity (EC50) of PLL on the addition of clay mineral--montmorillonite. A significant reduction (124%) in toxicity of the clay poultry litter leachate (CLL) after 7 days was observed compared to the toxicity of the PLL alone after 1 day. This indicates that some of the toxic components of the litter were adsorbed by the clay.