Background Most patients with obstructive sleep apnoea (OSA) do not tolerate treatment with nasal continuous positive airway pressure, the 'gold standard' treatment for this condition. It was shown in a pilot study that acupuncture was more effective than placebo treatment (sham acupuncture) in producing signifi cant changes in the respiratory events assessed by polysomnography (PSG). Objectives To investigate the immediate effect of manual acupuncture (MA) and electroacupuncture (EA) on the sleep pattern of patients presenting with moderate OSA. Methods 40 patients with an Apnoea-Hypopnoea Index (AHI) of 15-30/h were randomly allocated to MA treatment (n=10), EA 10 Hz treatment (n=10), EA 2 Hz treatment (n=10) and a no-treatment control group (n=10). The patients received MA or EA (2 or 10 Hz) just before the PSG study at 20:00. Results The AHI (p=0.005; p=0.005), the Apnoea Index (p=0.038; p=0.009) and the respiratory events (p=0.039; p=0.014) decreased signifi cantly in the MA and EA 10 Hz groups, respectively (AHI (21.9, 11.2), Apnoea Index (5.15, 0.7), respiratory events (120.5, 61.0) in the MA group before and after. AHI (20.6, 9.9), Apnoea Index (8.2, 0.3), respiratory events (117.0, 56.0) in the EA 10 Hz group before and after). The micro-arousals decreased only in the MA group (146.0 vs 88.5, p=0.0002). There were no signifi cant changes in the EA 2 Hz group or in the control group. Conclusion A single session of either MA or EA 10 Hz had an acute effect in reducing the AHI as well as the number of nocturnal respiratory events of patients presenting with moderate OSA.