We performed sleep studies in eight patients with multiple system atrophy (MSA) and three patients with peripheral bilateral vocal fold palsy (PBVFP) and investigated stenosis of the upper airway tract during sleep in MSA patients with vocal fold palsy. Among the eight MSA patients in this study, five had definite glottic snoring and two others were suspected of having glottic snoring. Of the PBVFP patients, two had glottic snoring. Three of 11 patients died, and two of the three deaths occurred during sleep. Glottic snoring indicated a high degree of negative esophageal pressure. High negative esophageal pressure demonstrates severe narrowing of the upper airway tract. Therefore, glottic snoring should be considered a risk factor for sudden death in sleep. Repeated laryngoscopic examination is useful in evaluating the progressive process of vocal fold palsy while awake, but this examination performed only while awake is not enough to evaluate narrowing of the upper airway during sleep. Sleep studies that include the measurement of esophageal pressure can be very useful in evaluating the severity of narrowing in the upper airway tract. It is suspected that sudden nocturnal death in MSA patients is caused not only by abnormal respiration resulting from impairment of the respiratory center, but also by glottic obstruction caused by sputum or by edema of the vocal folds. We recommend treatment of respiratory disorders when loud laryngeal snoring occurs in patients with MSA, even if they do not complain of dyspnea while awake.