The tongue-retaining device (TRD) was designed to increase the unobstructed dimension of the nasal breathing passage during sleep. Twenty male patients with diagnoses of sleep apnea syndrome, primarily of the obstructive type, confirmed by clinical polysomnography, were fitted with the device. The TRD holds the tongue in a forward position by negative pressure. Fourteen patients have been tested before and after this treatment, and ten of these have also completed two follow-up recordings four to six months after being trained in the use of this device. There was significantly improved sleep and significantly fewer and shorter apneic events on all nights when the device was worn. On the first night of wearing the TRD for a half night only, there was a significant reduction in the number of obstructive and central apneic episodes. The mean apnea plus hypopnea index while wearing the TRD is comparable with the rate reported for patients who have been treated surgically by either tracheostomy or by uvulopalatopharyngoplasty, although the tracheostomy group contained more severe cases.