Introduction Decompressive craniectomy  is a life saving procedure in patients with intractably raised intracranial pressure. The causes are many. The most common causes are  head injury, intracranial hemmorrhages, cerebral infarction, or malignant brain swelling due to any other cause.  Decompressive craniectomy aims primarily at the survival of patients and secondarily at the long–term quality of life. Aims and Objectives To analyze the functional outcome, complications and factors which predict the outcome of the patients who underwent decompressive craniectomy for the common causes of  brain swelling at Apollo Health City , Jubilee hills,Hyderabad, a tertiary care centre.     Materials and Methods In this prospectively designed study conducted from August 2010 to December 2012, decompressive craniectomy was performed in 112 patients. The 112 cases comprised of 40 traumatic brain injuries, 35 large hemispheric  infarcts  and 30 intracranial bleeds, (18 capsuloganglionic and 12 bleeds due to cortical venous thrombosis)   and  7 post operative brain swelling patients. All these patients were admitted in the department of neurology and neurosurgery at NIMS.  Patients having poor  Glasgow Coma Scale (GCS)  equal to 3,  diffuse axonal injuries(DAI),  with  severe comorbidities  and  those with primary brainstem injuries were excluded from the study. Detailed  neurological examination and  imageological studies  like Computed Tomography(CT) scan brain, Magnetic Resonnce Imaging(MRI)  brain whenever  necessary were performed in all patients. The variables that were studied  included patient’s age, sex, preoperative GCS, preoperative anisocoria, time of injury to surgery or time of deterioration to surgery, pre–operative risk factors and  post operative complications. Outcome assessed using modified Rankins Scale (mRS), Barthel index and Glasgow Coma Outcome Scale (GOS) at the time of discharge and at follow up of  3 and 6 months. The characters compared using SPSS version 17 software and Fisher exact test was used to compare proportions for categorical variables. A “p” value of less than or equal to 0.05 was considered statistically significant.    Results In traumatic brain injury patients, 31 out of (77.5%) patients had a good outcome (GOS more than or equal to 4).   In  stroke group, 17 out of 35 patients (48.57%) with cerebral infarction had a good outcome (mRS less than or equal to 3) while 10 out 18 patients (55.55%) with capsulo ganglionic bleed had a good outcome. out of 12 patients, 8 patients of CSVT  (66.66%)  had a good outcome.  7 patients, aneurysms (n=3), olfactory groove meningioma (n=1), sphenoidal wing meningioma (n=2), craniopharyngioma (n=1),     had  post operative brain swelling leading to conversion to decompressive craniectomy later on. Of these one patient died while one was in persistent vegetative state and two   were dependent. The chief complications across all groups were subgaleal collections(n=4), post operative seizures(n=4), pneumonia (n=10), abdominal wound site infection (n=4), hydrocephalus (n=3), syndrome of inappropriate secretion of anti diuretic hormone (SIADH) (n=7), sunken bone flap syndrome (n=1), renal failure (n=2), deep vein thrombosis (n=1), urinary tract infection (n=3) and sub galeal empyema (n=1). After analysis of multiple variables, we found  younger age, GCS more than 7, absence of anisocoria,  and surgical intervention less than 48 hours as factors affecting the good outcome (p <0.05).      Conclusions Decompressive  craniectomy is a life saving procedure.  Timely recognition of failure of medical management and an appropriately timed surgical intervention may  help to salvage  patients who develop malignant cerebral oedema and succumb to it. Younger age, pre–operative GCS more than 7,  absence of anisocoria and  intervention less then 48 hours after failure of medical therapy has shown a better outcome in this study. A large multi–centric study involving the more no of patients may help further in elucidating the factors predicting the outcome in various neurosurgical emergencies.