Expansion of intracranial contents by a space-occupying lesion (SOL) leads to compression and distortion of the tissues of the CNS and can increase Intrcranial pressure(ICP). It was presumed that ketamine can cause a dangerous increase in ICP by increasing blood pressure. The present study was conducted to investigate the effects of low doses of ketamine on ICP in patients having space occupying lesion of the brain. Methods The study was conducted on 45 patients after obtaining approval from ethical committee. Patients included were posted for elective supratentorial surgeries for brain tumour excision. Standard induction was done intravenously in all patients with Propofol, fentanyl and vecuronium with 5ml of normal saline(Group A), 0.25mg/kg ketamine diluted to 5ml (Group B) , 0.5mg/kg ketamine diluted to 5ml (Group C). Optic nerve sheath diameter(ONSD) measurement by ocular sonography which serves as an indirect non-invasive technique to measure ICP was recorded at 3 instances i.e. before start of IV boluses of drugs, at 2 mins of bag and mask ventilation and at 5 mins of post endotracheal intubation. Result ONSD values were comparable in all three groups at baseline. ONSD value decreased in all groups after 2 minutes of BMV and were comparable in all groups. Values slightly increased at 5 minutes after endotracheal intubation as compared to 2 minutes; though values were lesser than baseline in every group. Conclusion Our study refutes the old opinion that ketamine increases ICP. Combined with a benzodiazepine and barbiturate, ketamine may be the preferred sedative/anaesthetic agent for patients with space occupying lesion and can reduce ICP as well.