Accidental ingestion of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) was detected in an infant admitted at the Pediatric Emergency Department by drug testing in urine. Concentrations of MDMA and its principal metabolite 4-hydroxy-3-methoxymethamphetamine (HMMA) in the infant's hydrolyzed urine were 11.7 mg/L and 34.4 mg/L, respectively. Apparent febrile convulsions and cardiovascular side effects resolved within 1 day after treatment with benzodiazepines. Chronic exposure to cocaine was evidenced by segmental hair analysis. Continuous maternal denial of the presence of any drug in the household made diagnosis of accidental ingestion of MDMA and chronic exposure to cocaine problematic. Periodic clinical and laboratory follow-ups were requested to check eventual long-term effects of exposure to illicit drugs and discontinuation of the child from exposure to dangerous environments.