I read with interest the article entitled "Orthostatic intolerance ambulation in patients using patient controlled analgesia" in the recently published Korean Journal of Pain [1]. First, the phrase "orthostatic intolerance" was not familiar to me, and it also prompted me to give some attention to the postoperative patient in the ward after the postanesthesia care unit and to the patient's rehabilitation after surgery.In this article, the authors defined orthostatic intolerance (OI) as the occurrence of dizziness, nausea, vomiting, blurred vision, headache, drowsiness or syncope, and attempted to investigate the incidence of OI in gastrectomy patients during their first ambulation in their ward following surgery. The authors also tried to investigate the correlation between the incidence of OI and contributing factors. Although there are some questions relating to the settings of their study - the amount of infused opioids, pain measurements, etc. - I would like to express an opinion on the study's conclusions. The authors concluded that the incidence of OI is significantly higher in male than in female patients and that it is influenced by the opioid dose.Other studies have found that age, female gender, opioid use, or continuous infusion of fentanyl are predisposing factors for OI in some procedures [2-4]. Some of their results relating to fentanyl infusion are comparable to Park's report [3], but their findings on gender are not, as according to Park's study, the incidence of OI is higher in the male gender [1]. It is this result that I question in Park's article. The results compared the differences in patients who developed OI. Out of 105 patients who developed OI, 61 patients were male, and 44 patients were female, but their proportions out of the total male and female patients were 52.6% and 74.6%, respectively. With this result, I would perhaps conclude that the female gender is more vulnerable to OI than the male, as was shown in the other report [2].