Sleep disordered breathing (SDB) including obstructive and central sleep apnoea/hypopnoea as well as periodic breathing (PB) is common and is believed to increase risk for mortality in patients with congestive heart failure (CHF). Mandibular advancement device (MAD) has widely been recommended for treatment of obstructive sleep apnoea but the method has never been investigated for treatment of SDB in the patients with CHF. The aim with the present study was to examine the effect of MAD intervention on SDB in patients with CHF. The study included 17 male patients, aged 68.4+/-5.7 (mean+/-SD) with stable, mild to moderate CHF due to left ventricular systolic dysfunction and with SDB, expressed as apnoea/hypopnoea index (AHI) > or = 10. The SDB was examined during a single night using an unattended, portable polysomnographic device in the patients home, prior to and following intervention with a individually adjusted MAD. The SDB was evaluated by calculating AHI, PB expressed as the percentage of the total registration time, oxygen desaturation index (ODI) and snoring time. The AHI was reduced by MAD intervention from 25.1+/-9.4 to 14.7+/-9.7 (p=0.003). ODI reduced from 21.1+/-9.0 to 10.5+/-7.8 (p=0.007) and snoring time decreased from 53+/-111 to 18+/-47 seconds (p=0.02). PB was reduced from 55.7+/-25.6 to 40.4+/-26.4 per cent without statistical significance. In conclusion, the MAD intervention may be a feasible method for reducing SDB in patients with stable, mild to moderate CHF and left ventricular systolic dysfunction.