Oral activated charcoal (OAC) is a universally accepted treatment of the overdose patient. Although the benefits of OAC have been suggested, there are no conclusive clinical data indicating that OAC affects outcome in overdose patients. This study was a prospective, randomized, controlled trial to determine the effects of OAC treatment in the self-poisoned adult patient. Adult patients presenting to the emergency department (ED) with a history of oral overdose were assigned to treatment with OAC (50 g) or supportive care only on an even-odd day protocol. Patients did not undergo gastric evacuation procedures in the ED. The outcome measures were clinical deterioration, length of stay in the ED or hospital, and complication rate. Over a 24-month period, 1479 patients were entered into the study. There were no significant differences in outcome parameters between the OAC treatment group and controls when comparing the length of intubation time, length of hospital stay, and the complication rates associated with the overdose. There was a higher incidence of vomiting and longer length of ED stay associated with OAC treatment. The results of this study indicated that oral drug overdose patients do not require gastric evacuation or charcoal administration. OAC provided no additional benefit to supportive care alone, was associated with a higher incidence of vomiting and a longer length of ED stay, and did not improve clinical outcome.