A case of acute Dapsone intoxication due to voluntary ingestion of 3 g of this drug as a suicide attempt is described. A severe methemoglobinemia developed, accompanied by intense cyanosis, dyspnea, headache, and nausea. Subsequently, significant sulfhemoglobinemia responsible for prolonged cyanosis was observed, as well as mild hemolytic anemia. Relapses of methemoglobinemia after methylene blue treatment required repeated administration of the reducing agent. The need of a careful follow-up for several days in this type of intoxication is emphasized.