BACKGROUND: This prospective study of 40 patients who underwent diagnostic laparoscopy at outpaient surgery center was performed to assess the use of ketamine as a analgesic adjuvant during intravenous anesthesia with propofol compared with the combination of propofol-fentanyl. METHOD: Anesthesia was induced with propofol (2 mg/kg) and either fentanyl (1 microgram/kg) or ketamine (0.2 mg/kg). Anesthesia was maintained with propofol 200 microgramkg-1min-1 during the first 5 min, followed by 180 microgram/kg 1min 1 for 5 min and then 160 microgram/kg-1min-1 after 10 min. The patient's lungs were mask ventilated with 50% N2O-O2. Increments of propofol were given during anesthesia if analgesia was judged to be inadequate. RESULT: Stable arterial pressure and heart rate were seen in the patients of both groups, except for a temporary increase of heart rate after induction of anesthesia in ketamine group. There were no significant differences between ketamine and fentanyl groups in total dose of propofol, response time, recovery time or VAS at 30 min after operation. Patients who received propofol-ketamine demonstrated a longer discharge time than the patients received propofol-fentanyl. There were higher incidences of dizziness and 1 patient showed emergence delirium in patients given propofol-ketamine, other side effects were similar. CONCLUSION: We concluded that low-dose ketamine with propofol can replace propofol-fentanyl for intravenous outpatient anesthesia.