We describe the effects of different tracheostomy techniques on intracranial pressure (ICP), cerebral perfusion pressure (CPP), and cerebral extraction of oxygen. We attempted to identify the main mechanisms affecting intracranial pressure during tracheostomy. To do so we conducted a prospective, block-randomized, clinical study which took place in a neurosurgical intensive care unit in a teaching hospital. The patients studied consisted of thirty comatose patients admitted to the intensive care unit because of head injury, subarachnoid hemorrhage, or brain tumor. Ten patients per group were submitted to standard surgical tracheostomy, percutaneous dilatational tracheostomy or translaryngeal tracheostomy. In every technique a significant increase of ICP (P < .05) was observed at the time of cannula placement. Intracranial hypertension (ICP > 20 mm Hg) was more frequent in the percutaneous dilatational tracheostomy group (P < .05). Cerebral perfusion pressure dropped below 60 mm Hg in eleven cases, more frequently during surgical tracheostomy. Arterial tension of CO2 significantly increased in all three groups during cannula placement. No other major complications were recorded during the procedures. At follow-up no severe anatomic or functional damage was detected. We conclude that the three tracheostomy techniques, performed in selected patients where the risk of intracranial hypertension was reduced to the minimum, were reasonably tolerated but caused an intracranial pressure rise and cerebral perfusion pressure reduction in some cases.