ABSTRACT A 14-year-old boy with attention-deficit/hyperactivity disorder was prescribed desipramine for over 12 months, and had been generally stable on 300 mg daily at the time of his death. Three months before, his plasma desipramine level was 132 ng/mL while taking 225 mg daily. Family history included cardiac disease but not sudden death. After diving in a pool for several minutes, he climbed out of the pool, sat down, and lost consciousness. Witnesses described body movements that might have been a seizure. Despite extensive resuscitation, the patient died within 1 h. There was no evidence of acute or chronic overdose, suicidality, pill hoarding, or missing pills. Autopsy uncovered an anomaly in the size of the right coronary artery. This is the fifth reported case of sudden unexplained death of a youth during tricyclic antidepressant treatment that is not attributed to overdose. All five cases have involved desipramine, and three occurred during or just following physical exertion. Despite ample ava...