There is currently much interest in the use of decompressive craniectomy for intracranial hypertension. Though technically straightforward, the procedure is not without significant complications. A retrospective analysis was undertaken of 164 patients who had had a decompressive craniectomy for severe head injury in the years 2004 to 2009 at the two major hospitals in Western Australia. Eighty-six patients had a bifrontal decompression and seventy-eight had a unilateral decompression. Two patients died due to post-operative care issues. Complications attributable to the decompressive surgery were: herniation of the cortex through the bone defect (42 patients, 25.6%), subdural effusion (81 patients, 49.4%), seizures (36 patients, 22%), hydrocephalus (23 patients, 14%), and syndrome of the trephined (2 patients, 1.2%). Complications attributable to the subsequent cranioplasty included: sudden death due to massive cerebral swelling in 3 patients (2.2%), infection requiring removal of the bone flap in 16 patients (11.6%), and bone flap resorption requiring augmentation in 10 patients (7.2%). After excluding simple complications such as subdural effusion and brain herniation through the skull defect and some patients who died as a direct consequence of traumatic brain or extracranial injury, 81 patients (55.5%) had at least one complication after decompressive craniectomy. The occurrence of at least one complication after decompressive craniectomy was significantly associated with an increased risk of prolonged stay in the hospital or rehabilitation facility (odds ratio 2.54, 95%confidence interval 1.22,5.24, p=0.013), after adjusting for predicted risk of unfavorable outcome.