We investigate sleep and breathing in clinically stable myasthenia gravis (MG) patients and ask weather sleep disordered breathing (SDB) is causally linked with MG. Nineteen MG patients with a mean disease duration of 9.7 years underwent sleep studies in two consecutive nights. The primary outcome measure was the respiratory disturbance index (RDI) in terms of snoring and apneas/hypopneas. Further outcome measurements were total sleep time, sleep stage distribution and the number of arousals. A clinically relevant SDB in terms of obstructive sleep apnea (OSA) (defined as RDI > 10/h) was found in four patients. There were only a few central apneas (central apnea index: 0.19 +/- 0.4/h). We did not find a relationship between maximum inspiratory pressure and SDB (r = -0.03). There is no evidence for a causal relationship between medically stable MG and SDB in terms of OSA. The extent of respiratory muscle weakness failed to correlate with SDB. Furthermore, our study does not confirm the high occurrence of central respiratory events during sleep in patients with well-controlled MG.