The many kinds of complication that have been observed following operations of basilar impression and/or malformation of Arnold-Chiari are analysed. Two surgical techniques were adopted in the treatment of the patients. In the first 64 cases, the operation consisted in the craniectomy of the posterior fossa and high cervical laminectomy, while the dura-mater remained opened and suturated to the lateral musculature. Concerning the other 75 cases, it was made a plastic of the dura-mater of the posterior fossa and, in most of the cases, the patients were intubated with no retroflexion of the head and operated in sitting position without anterior flexion of the head. In the second group of patients, it was observed lesser occurrence of complications and death.