BACKGROUND Moebius syndrome is an infrequent congenital, non-progressive disorder that is defined by facial palsy (usually bilateral) and oculomotor compromise. Its clinical spectrum is variable but it affects other cranial nerves and is associated with multiple malformations. METHODS We report the clinical, neurological and neuroimaging features and the progress of 20 patients (16 males and 4 females) who satisfied diagnostic criteria for Moebius sequence. RESULTS Ages at the first visit ranged from 9 days to 23 months. Births had been normal in 50% of the patients. Facial nerve compromise was observed in all cases, 70% being bilateral. Cranial nerves VI (85%), XII (40%), VIII (25%) and IX (60%) were also involved. Perinatal respiratory distress was seen in 35% of the patients, apnoeas in 25% and retarded development in 60% of cases. They also presented other associated malformations such as microretrognathia, ogival palate, club foot, hand and foot malformations, and four cases presented unilateral agenesis of the pectoralis major. An electromyogram study showed absence of spontaneous and voluntary activity and muscle evoked potentials on stimulating the facial nerve; magnetic resonance imaging of the brain showed hypoplasia of the trunk, agenesis of the cranial nerves and abnormalities in the posterior fossa in three of the ten cases in which the scan was performed. CONCLUSIONS The association of multiple malformations and dysfunction of the cranial nerves suggests a disruption in the process of morphogenesis during the embryonic period, and therefore Moebius syndrome is considered to be a malformative sequence.