The surgical technic for decompression of the posterior fossa in cases of basilar impression and malformation of Arnold-Chiari mainly based in (1) endotracheal intubation without any flexion of the head, (2) position of the head without anterior flexion during the surgery, (3) plastic of the posterior fossa with dura-mater of cadaver conserved in glicerina, was emploied in 13 patients. The plastic was made to create space at the craniocervical joint in order to avoid cerebrospinal fluid fistula and to restore the integrity of the dura. Infection was not observed.