The ability of activated charcoal to adsorb ochratoxin A (OA) in vitro and to reduce the toxic effects of OA in vivo when added to the diet of growing Leghorn chicks was studied. Activated charcoal (50 mg) was able to adsorb 90% of the OA (150 micrograms) contained in 10 mL of citrate-phosphate buffer (pH 7.0). When 2 g of a complete chick diet were mixed with OA in buffer, it adsorbed 66% of the OA, while addition of 50 mg of charcoal to this mixture further reduced the concentration of OA to 11.8% of the control, an additional 65% compared to the diet alone. In the first of two feeding studies, charcoal addition of up to 10,000 parts per million (ppm) to diets (6.7% tallow) containing 9.93 mumol (4 ppm) OA kg-1 diet had no effect on OA toxicity. Feed consumption and weight gain, however, were reduced 10 and 20%, respectively, in chicks fed diets which contained 10,000 ppm of charcoal compared to those fed no charcoal. In the second study, reducing dietary tallow to 2% did not alter the effects of OA or charcoal on weight gain and feed to gain ratio, but birds fed OA with 10,000 ppm charcoal had an 8.5% increase in feed consumption. An additional management problem was associated with the propensity of charcoal to blacken the feed, the birds and their environment. Addition of charcoal to OA contaminated diets appeared to be an ineffective method for reducing the toxic effects of OA in growing chicks.