SummaryChemotherapy for malignant tumors has diversifi ed, and recognizing its side effects has become more important than ever. Both cardiotoxicity and neurotoxicity are rare, but they are among the most serious side effects caused by 5-fl uorouracil (5-FU). Capecitabine is an orally administered prodrug that converts preferentially to 5-FU within tumors, resulting in enhanced concentrations of 5-FU in tumor tissue. Given that it targets tumor tissue, capecitabine was expected to reduce the risk of side effects associated with fl uoropyrimidine. Here, we present the case of a 62-year-old man with colorectal adenocarcinoma who simultaneously experienced cardiomyopathy with cardiogenic shock and cerebral leukoencephalopathy during treatment with capecitabine. During emergency coronary angiography, ST-segment elevation and severely reduced left ventricular wall motion were observed; however, no severe coronary stenosis or spasm was revealed. Furthermore, we present a review of the literature on capecitabine-induced cardiotoxicity. As of April 2013, 39 case reports on capecitabine-induced cardiotoxicity have been published; however, cardiomyopathy was very rare, with only 3 cases reported. It is important for physicians to be aware of the various rare, but potentially serious, adverse effects associated with capecitabine chemotherapy and to inform patients about the possibility of these side effects, including cardiotoxicity and neurotoxicity. (Int Heart J 2013; 54: 417-420) Key words: Chemotherapy, Cardiotoxicity, Neurotoxicity R ecently, chemotherapy for malignant tumors has diversifi ed, and recognizing the side effects of chemotherapy as well as its curative effects has become more important than ever. Many anticancer drugs are cardiotoxic, and it is well known that both anthracycline antibiotics and trastuzumab cause congestive heart failure.1) Five-fluorouracil (5-FU) is one of the most important chemotherapeutic agents used to treat many solid tumors, including colorectal cancer; however, it has several adverse effects.2) Cardiotoxicity 3) and cerebral leukoencephalopathy 4) are rare side effects of 5-FU therapy, but are among the more serious side effects associated with this therapy. Capecitabine, an orally administered fl uoropyrimidine carbamate, is a 5-FU prodrug that was developed to lessen the side effects associated with 5-FU therapy.5) Oral 5-FU often causes intestinal tract toxicity, and oral administration of high-dose 5-FU raises the concentration of the drug in the intestinal tract; therefore, intestinal tract toxicity is often the dose-limiting factor. Capecitabine itself is not cytotoxic, but it becomes effective after it has been converted to 5-FU in tumor cells. 5,6) It is widely used because it can be orally administered and is associated with fewer side effects.2) However, as the use of capecitabine becomes more widespread, its side effects, including cardiotoxicity, appear to be similar to those of 5-FU.3,7) We report a case of cardiomyopathy mimicking acute coronary syndrome that coin...