Tracheal sound recordings and O2 saturation were compared with conventional recordings of respiratory events (thermistors, strain gauges, and O2 saturation) in 14 patients referred for assessment of sleep apnea syndrome. There was no significant difference in the number of respiratory events associated with desaturation recorded during the sleep by the two methods. Tracheal sound recordings were more useful in analyzing the cause of the respiratory event. Hypopnea without desaturation was seen more often with tracheal sound recordings than with the conventional methods. The durations of apneic and hypopneic events were significantly longer when recorded by thermistors and strain gauges than by breath sounds.