Use of Ondensetron (antiemetic) is quite common practice before giving Tramadol (analgesics).Many of the ED patients present with pain and Tramadol is the drug of choice for us. It is usually given intravenously. This is an Opoid analgesic and acts via binding to the mu opioid receptor, but also inhibits the reuptake of serotonin and norepinephrine due to its action on the noradrenergic and serotonergic systems, such as its “atypical” opioid activity. Vomiting is due to central stimulation of CTZ and by peripheral labrynthine stimulation. A major proportion of patients presenting to our emergency department have various painful conditions. In our department, tramadol has been the intravenous opioid of choice. In our experience, the advantages of IV tramadol are its titratability (dose range 1-2 mg/kg) and predictability. Traditionally, it has been the norm to use prophylactic antiemetics along with opioids to counter their emetic side effects.All opioids have the well recognised side effects of nausea and vomiting, with some being worse than others. These symptoms are mediated both centrally, by stimulation of the chemoreceptive trigger zone and dopamine receptors in the medulla, and peripherally, by labyrinthine stimulation and reduced gastric emptying. Thus antiemetic prophylaxis is particularly common with the use of opioids for acute pain,and also in postoperative acute pain, where the incidence of nausea and vomiting varies between 8% and 92%.It is a normal practice in our ED to give prophylactic ondensetron before giving tramadol for prevention of vomiting.This sole aim of this work was to find out how far the practice of using prophylactic antiemetic before opioid was correct and how effective it was in preventing nausea and vomiting.