SUMMARYCardiac risk factors are observed more frequently in patients with polycystic ovary syndrome (PCOS). On the other hand, increased QT dispersion, which is a risk factor for cardiac arrhythmias and sudden death, has not been investigated in this syndrome. In this study, we evaluated QT dispersion in PCOS patients without overt heart disease. Thirtysix consecutive women with PCOS (mean age 24±5 years) and 36 healthy women of similar ages (mean age 24±4 years) participated in this study. PCOS was diagnosed if there were polycystic ovaries by ultrasound (enlarged ovaries with ≥8 cysts 2-8 mm in diameter), oligoamenorrhea (intermenstrual interval >35 days), hirsutism (Ferriman-Gallwey score, ≥7) and elevated serum levels of testosterone (≥2.7 nmol/L). Electrocardiograms were recorded at a paper speed of 50 mm/s. QT intervals were manually measured by a cardiologist. All intervals were corrected for heart rate according to Bazett's formula: QTc interval=QT interval/square root of the RR interval. Mean values of body mass index, heart rate, and blood pressure were not significantly different between the two groups (P>0.05). No significant differences in QT intervals (maximum QT, minimum QT, QT dispersion, minimum corrected QT, maximum corrected QT, and corrected QT dispersion) were observed between the two groups (P>0.05). Our results suggest that the risk of ventricular arrhythmias or sudden cardiac death is not increased in PCOS patients. (Jpn Heart J 2002; 43: 487-493) Key words: Electrocardiography, Polycystic ovary syndrome, QT dispersion POLYCYSTIC ovary syndrome (PCOS) is a disorder of chronic anovulation, hyperandrogenism, hirsutism, obesity, subfertility, hyperlipidemia, and insulin resistance. Infertility is not the only important component of this syndrome, since the risks of cardiac disease and hypertension also increase in women with PCOS.1-3) Insulin resistance and hyperinsulinemia appear central to the pathophysiology of PCOS. Glucose intolerance, abnormally high fasting serum lipid concentrations, and high blood pressure are the three cardiac risk factors that have From the