The case is reported of a non-diabetic young woman who attempted suicide by ingesting 2,500 mg of phenformin. The most marked clinical and laboratory findings during the first 24 hrs included nausea, vomiting, anxiety, agitation, polydipsia, polyuria, increased appetite, tachycardia, tachypnea, persistent lactic acidosis, hypoglycemia and hypokalemia. Treatment at the ICU 10 hrs after ingestion of the overdose was essentially symptomatic and included measures to correct acidosis and hypoglycemia. The patient recovered completely.