Present study was carried out in randomly choosen 150 patients of ASA grade­I and grade­II having neither respiratory nor cardiovascular diseases, no obecity.Study included children, adult as well as middle age group posted for various surgical operations under general anaesthesia.The aim of study was to detect early up to one hour postoperative hypoxemia by continuous monitoring of oxygen saturation by pulse oximetry and role of oxygen therapy to treat the hypoxemia. In our study base line hypoxemia was taken at SaO2 92%.All patients were premedicated with i.v atropine/ glycopyrollate, i.v diazepam, i.v fortwin and was induced with i.v thiopentone sodium or ketamine hydrochloride and endotracheal intubation was done under effect of suxamethonium and anaesthesia was maintained on oxygen + nitrous oxide + i.v norcuron+intermittent halothane for few patients with controlled ventilation.At the end of surgery all patients were extubated after reversal with i.v neostigmine and i.v atropine/i.v glycopyrollate and observed on operation table for first 15. min without supplementation of oxygen to detect the incidence of early postoperative hypoxemia. In first 15 min . Out of 150 patients 53(35.33%) patients became hypoxemic and were treated with supplementation of 4lit/min 100% oxygen through face mask for 15 min.on operation table, then shifted in recovery room which was very near to operation theatre. All patients those who received oxygen as well as not received were observed in recovery room up to one hour. Out of 53 patients only 3 patients became hypoxemic in second episode in between 16 to 30 min.and were treated as above then not a single patient became hypoxemic.