The purpose of the present investigation was to examine the relationship among upper airway resistance, snoring, and arousals, all measured simultaneously, in nonapneic snorers complaining of excessive daytime sleepiness (EDS). To accomplish this task, we selected a group of nine nonapneic snorers who presented because of snoring, EDS, tiredness, or fatigue. Ten healthy, alert, nonapneic, nonsnoring subjects recruited from among the hospital personnel acted as a comparison group. All subjects had nocturnal polysomnography, which included measurements of snoring, nasal and pharyngeal airway pressure, esophageal pressure, and total respiratory flow. Each polysomnogram was analyzed to identify all arousals and all respiratory events, i.e. apneas, hypopneas, and periods of increased upper airway resistance. Each arousal was examined to determine whether it was associated with a respiratory event, and each respiratory event was examined to determine whether it was associated with an arousal. The results were compared between snorers and nonsnorers. There was no significant difference between the two groups in the total sleep time (182+/-61 minutes in controls vs. 188+/-50 minutes in patients) or the total number of arousals per hour of sleep (24+/-12 in controls vs. 28+/-10 in snorers). However, the distribution of arousals, i.e. electroencephalogram (EEG) vs. respiratory, was different in snorers and nonsnorers. In snorers 55% of arousals were respiratory, whereas in nonsnorers only 17% of arousals were associated with respiratory events. Not unexpectedly, the snorers had significantly more respiratory events during the night (512) than controls (112). However, the relative proportion of these events that was accompanied by arousals was similar in both groups. We conclude that the difference in daytime function between symptomatic snorers and asymptomatic nonsnorers is unlikely to be due strictly to the number of arousals during the night; however, it is possible that respiratory and EEG arousals have different impacts on daytime performance, which may explain the difference in daytime function between our two groups.