We present a case of acute lethal poisoning by oil of "epazote" (oil of chenopodium), in a 2 y 9 m female. The volatile oil was administered according to the advice of a "curandera" (female healer), in a total quantity of 40 ml. Clinical features of the poisoning were: vomiting, deep coma, seizures, mydriasis, apnea, metabolic acidosis, neurogenic shock and death. The EEG suggested a diffuse encephalopathy, the CT scan with an image of severe brain edema and ventricular collapse. Relevant postmortem findings were brain edema and neuronal necrosis, pneumonia, enteritis, pericholangitis, mild pancreatitis and tubular necrosis. The phytochemical analysis of volatile oil identified ascaridol, the main active compound of the chenopodium herbs, in a quantity of 39 mg/ml (1,560 mg in the dose administered), and Chenopodium graveolens as the plant employed to prepare it. According to the age of the patient, 60 mg of ascaridol would be the recommended dose formerly used in the treatment of parasitic disease. Thus 1,560 mg was 26 times higher than the recommended dose, and exceeded by 56% the dose of 1,000 mg reported as lethal in humans.