OBJECTIVE The purpose of this study was to assess sleep and breathing in patients with amyotrophic lateral sclerosis (ALS) with bulbar muscle involvement. METHODS Prospective, controlled study of sleep and breathing measured during polysomnography. METHODS University teaching hospital and referral center. METHODS Patients with definite ALS and healthy age-matched control subjects. METHODS Eighteen ALS patients and 10 age-matched control subjects underwent one night of polysomnography. Thirteen patients with ALS were studied for a second night. RESULTS The ALS patients had more arousals per hour (p = 0.008), more stage 1 sleep (p = 0.01), and a shorter total sleep time (TST) (279 +/- 69 vs 331.4 +/- 55.9 min, mean +/- SD, p = 0.04) than the control subjects. The ALS patients had mild sleep-disordered breathing with a greater apnea/hypopnea index (AHI) than the control subjects (p = 0.005). On the second night of polysomnography, there was an increase in TST (p = 0.003) and rapid eye movement (REM) sleep (p = 0.009), an improvement in sleep efficiency (p = 0.02), and less stage 1 sleep (p = 0.04). Eight ALS patients had sleep-disordered breathing consisting of periods of hypoventilation, predominantly during REM sleep. CONCLUSIONS Sleep-disordered breathing occurs in patients with ALS and is similar to patients without ALS with respiratory muscle weakness. No obstructive sleep apnea was observed. One potential reason for its absence might be the inability of patients with respiratory muscle weakness to generate an inspiratory pressure greater than the upper airway closing pressure. This hypothesis should be addressed in future studies.