QT prolongation is associated with a poor prognosis in patients with various diseases. The pathogenesis of the long QT syndrome is not well understood and little is known about the QT interval in the patients receiving maintenance hemodialysis. We evaluated changes in the QTc interval and investigated factors that contribute to its prolongation in 42 patients receiving maintenance hemodialysis. We also examined the association between the QTc interval and ventricular arrhythmias on 24-h ambulatory electrocardiograms. Comparison of standard 12-lead electrocardiograms of 42 patients and of 30 healthy controls matched for age and sex showed that the QTc interval in the patients was significantly prolonged (432.6 +/- 24.9 vs 402.0 +/- 21.0 ms, p <0.001). Multivariate analysis using stepwise multiple regression identified diabetes mellitus and the ejection fraction measured by echocardiography as independent risk factors for QTc prolongation. The QTc interval was significantly prolonged in patients with complex VPCs (couplets or salvos) (n = 13, 447.9 +/- 14.4 ms) on 24 h ambulatory ECG compared with simple VPCs (none or occasional) (n = 29, 425.6 +/- 25.8 ms) (p = 0.03). In conclusion, the QTc interval was prolonged in patients receiving maintenance hemodialysis and QTc prolongation was associated with complex VPCs. Decreased myocardial contractility and diabetes mellitus contributed to QTc prolongation.