The sitting position offers the benefits of better access to the apex of the posterior fossa, and an improved exploration and dissection because blood and cerebral spinal fluid drain away from the operative site. Specific complications of the sitting position include cardiovascular instability, jugular venous obstruction, airway oedema, quadriplegia, displacements of catheters and the endotracheal tube, ulnar, sciatic and lateral peroneal nerve compression, venous air embolism, and tension pneumocephalus. In the only existing comparative study, the differences were an increased bleeding in the horizontal position and a better cranial nerve presentation in the sitting position. This argues strongly for teaching and use of the sitting position whenever surgically indicated. (C) 1998 Elsevier, Paris.