Two female epileptics, 19 and 27 years old, were admitted after ingestion of an overdose of sodium valproate. The patients were comatose for 6 and 7 days and required mechanical ventilation for 7 and 10 days. Both patients were in deep coma for several days after serum concentrations had dropped into the therapeutic range. Serum concentrations of sodium valproate were 3348 mumol/L (482 mg/mL) in one patient and more than 10,000 mumol/L (1440 mg/mL) in the other. Drug elimination followed first order kinetics, and the plasma half-lives of sodium valproate were 19 and 20 hours, respectively. Their anemia, leucopenia and thrombocytopenia required transfusion. Liver enzymes were only moderately elevated, but one of the patients developed acute pancreatitis. There were no apparent sequelae two weeks after discharge from the hospital.