A 19-year-old patient intending to commit suicide gave himself an intravenous injection of about 14 g methyliodide. The patient was admitted to our hospital in a state of somnolence and agitation followed by a cerebral convulsion and severe hypotension. The serum concentration of methyl iodide was measured by mass spectroscopy. In addition to an antidote therapy with acetylcysteine, haemoperfusion was performed followed by a remarkable decrease of the methyliodide concentration. The patient survived this severe intoxication and was discharged from the hospital after a week.