We describe three patients with a complex syndrome of apparent arthromyodysplasia, dyscephaly, sacral agenesis, and hypoplastic digitis. Cause is unknown, but an environmental cause is suspected on the basis of ergotamine exposure in one case and diazoxide intake in another, together with suggestive similarities to anomalies seen in animals treated with these drugs and to calves with the Australian hydranencephaly/arthrogryposis syndrome caused by Akebane or Aino virus. Pathogenetically the primary defect may be a neural tube-neural crest dysplasia with multiple secondary and tertiary manifestations and deformities.