The development of a gastrointestinal obstruction associated with multiple doses of activated charcoal is described. A carbamazepine-intoxicated patient received 240 g of activated charcoal and a total of 600 mL magnesium citrate with the development of an ileus and a small-bowel obstruction. The patient also had episodes of emesis associated with charcoal administration. This case suggests that the use of multiple doses of activated charcoal may be associated with gastrointestinal obstruction, a previously unreported adverse effect. Further evaluation of the incidence of adverse effects associated with activated charcoal is needed to determine optimal therapeutic regimens.