A fatal monointoxication with diphenhydramine in a male 28 year old is reported. The patient went into hyperpyrexia and tachycardia and died from sudden cardiac arrest. Hemorrhagic pulmonary edema and renal shock were the most prominent pathomorphological findings. At the time of death, the concentration of diphenhydramine was 5 mg/l plasma and was particularly high in the lungs (55 mg/kg) and kidneys (50 mg/kg).