An autopsy case of carbamazepine overdose with focal myocarditis is reported. The decedent was a 33-year-old female with a history of schizophrenia and bipolar disorder, who reportedly took 5-day dose of prescribed medications at around midnight. Although she stayed home following the direction of the physician, she was pronounced dead 8h after the intake. At autopsy she was obese, and her face was slightly swollen. The 420 g heart was free of coronary atherosclerosis, and the myocardium had no obvious scars. Both the left and right lungs were markedly congested and edematous. Strong congestion was also noted in the brain and visceral organs. Microscopic examination disclosed focal infiltration of inflammatory cells, most of which were lymphocytes, into the myocardium. In the toxicological analyses, carbamazepine concentration in the blood was 9.9 microg/ml, and other medications were below the toxic levels. It was considered that under the compromised cardiac function due to myocarditis presumably induced by some prescribed medications, and obesity, the carbamazepine overdose deteriorated her condition by triggering critical arrhythmia or congestive heart failure.