Sodium nitrite is used commercially as a coloring agent, a food preservative and a corrosion inhibitor. Accidental poisoning usually results from the ingestion of contaminated food and water and causes gastrointestinal irritation, vasodilatation and methemoglobinemia with subsequent tissue hypoxia. We describe an unusual case of sodium nitrite-induced methemoglobinemia following the ingestion of drinking water contaminated with a corrosion inhibitor. To our knowledge this is the first report of such a case.