Mobius sequence/syndrome is a rare disorder characterized by congenital palsy of the 6th and 7th cranial nerves. Other cranial nerves may be affected, skeletal and orofacial anomalies and mental retardation occur. The aims were to determine the frequency of associated clinical characteristics and to identify any pregnancy or environmental factors in patients with Mobius sequence. A prospective study of 25 Swedes with apparent involvement of the 6th and 7th cranial nerves was performed and 25 patients, 1 month to 55 years old, were examined. Obvious associated systemic anomalies observed included: limb malformations (10), Poland anomaly (2), hypodontia (7), microglossia (6), cleft palate (4), hearing impairment (5) and external ear malformation (1). Pronounced functional abnormalities were observed involving facial expression (16), speech (13), eating and swallowing (12) and difficulty in sucking in infancy (11). Six patients had an autistic syndrome, one an autistic-like condition, and mental retardation was found in all these patients. No common aetiological cause was found but their mothers' pregnancy histories revealed a history of benzodiazepines (1), bleeding during pregnancy (8), spontaneous abortion (7) and chorion villus sampling in the second month of pregnancy (1). In conclusion, many patients had multiple problems with eating and communication resulting from facial palsy, cleft palate and tongue anomalies. Autism and mental retardation was diagnosed in one-third of the patients. Awareness of the wide spectrum of manifestations in Mobius sequence will assist in identification of the associated malformations and functional problems that are often seen and result in better care of the children.