The aim of this study was to estimate the incidence of postoperative vomiting (POV) in patients undergoing operations under general anaesthesia, as well as the application of a simple risk score for prediction of POV. Four hundred thirty one patients scheduled to undergo four different kinds of surgical procedures under general anaesthesia (mastectomy, thyreoidectomy, abdominal hysterectomy, laparoscopic cholecystectomy) were included in the study. The incidents of POV were recorded at two different periods: 1) early period: during the first hour after recovery from general anaesthesia in the PACU, 2) delayed period: during the rest twenty-four hours in the ward. Every patient scored according to a risk score, which developed by Apfel et al, ranged 0-4 (one degree for each criterion: female sex, no smoking, history of POV, administration of opioids) to evaluate the probability of predicting POV from its application. The results showed that the incidence of POV was significantly shorter (p<0,001) at the early period as well as there was a relationship (p<0.001) between the allocation of POV incidence in this study and the Apfel’s risk score, approved that patients with a high score had a grater incidence of POV. Conclusively the incidence of POV in these surgical procedures is small at the first hour after recovery and significantly greater at the rest of the day. The more degrees of Apfel’s risk score the greater the incidence of POV.