Measurement of serum osmolal gap is a useful tool in suspected toxic alcohol ingestion. Normal levels of osmolal gap are typically <10 mOsm/kg). Osmolal gap >20 mOsm/kg is usually caused by ingestion of methanol, ethylene glycol, isopropanol, propylene glycol, diethylene glycol, or organic solvents such as acetone but rarely of ethanol alone. Herein, we describe the case of a severe ethanol intoxication presenting with a marked increase in the osmolal gap. An 18-year-old male was referred to the emergency department of our hospital, in a comatose state, following binge drinking. blood gas analysis revealed a high anion gap metabolic acidosis. In addition, it was found an extremely elevated osmolal gap of 91 mOsm/kg. The increment of the osmolal gap and the high anion gap acidosis could not be attributed to methanol/ethylene glycol intoxication, alcoholic ketoacidosis, or other cause of acidosis. The calculated osmolal concentration of ethanol was 91 mOsm/kg (osmolal concentration of ethanol is equal to the serum ethanol levels (mg/dL) divided by 3.7). Thus, the increase in the osmolal gap was a result of ethanol intoxication solely. Acute, isolated, ethanol intoxication may be a rare cause of a marked increase of osmolal gap with high anion gap metabolic acidosis. Clinicians should be alerted to the possibility of acute ethanol intoxication in a patient presenting with high anion gap metabolic acidosis and an extremely elevated osmolal gap. Toxicologic screen tests should be performed to identify the aetiology of the gap rise and proper therapy should be administered.