The relationship between arrhythmias and sleep states was investigated in patients with night-type arrhythmias, which were detected by 24-hour electrocardiogram recordings using the Holter Avionics system. These patients were examined using all-night polygraphic recordings and sleep states were divided into 5 groups according to the standard sleep stage scoring manual as stage I, II, III, IV, and REM sleep. Patients were divided into 5 groups: (1) grade 2 ventricular premature contractions (VPCs), (2) grade 4a VPCs, (3) grade 4b VPCs, (4) supraventricular premature contractions, and (5) paroxysmal tachyarrhythmias such as paroxysmal atrial fibrillation or paroxysmal supraventricular tachycardia. The paroxysmal tachyarrhythmia group showed a significant increase in arrhythmia incidence during REM sleep (p<0.05). However, the subjects with other arrhythmias showed no significant increase during REM sleep, but grade 2 VPCs showed a tendency to increase in sleep stage IV (0.05<p<0.1). These results suggest that there are 2 types of arrhythmias influenced by sleep. The first type is affected by a phasic increase in sympathetic nervous tone during REM sleep and the second type is related to an increase in vagal tone during the night.