Introduction: Primary dysmenorrhea (PD), which is characterized by painful menstrual cycles, is one of the common clinical problems in young adult women. The aim of this study was to investigate the risk of cardiac arrhythmias in PD patients by using the electrocardiographic (ECG) parameters. Methods: Forty patients diagnosed with PD and 30 age-matched normal controls were included in this study. ECGs were performed by using 12-leads with 10 mV amplitude and 25 mm/sec velocity. P and QT waves were manually marked along the isoelectric line. P maximum, P minimum, QT maximum and QT minimum were measured on the surface 12-leads ECG, and the P wave and QT dispersions were calculated. Results: There was not any significant correlation of P wave dispersion and QT dispersion between the age, sex, body mass index, hemoglobin, fasting blood glucose or any other laboratory parameters. P wave dispersion was significantly longer in the PD group than the control group (61.4 +/- 19 msec versus 57 +/- 14 msec, P = 0.01). The P minimum duration was significantly shorter in the PD group compared with the control group (36 +/- 16 msec versus 41 +/- 9 msec, P = 0.03). QT dispersion was significantly higher in the PD group compared with normal controls (76 +/- 23 msec versus 58 +/- 16 msec, P = 0.02). Conclusion: These results show that PD can be associated with cardiac arrhythmias, especially atrial fibrillation, by increasing P wave dispersion and ventricular arrhythmia risk because of an increased QT interval.