['To evaluate the antiemetic effect of iv dexamethasone for preventing postoperative nausea and vomiting (PONV) in women with and without a history of motion sickness.', 'This randomized, double-blinded, placebo-controlled study was carried out in 168 female patients with (n = 84) and without (n = 84) a history of motion sickness undergoing gynecological laparoscopy. Patients received 8 mg dexamethasone or saline immediately before induction of anesthesia. Postoperatively patients were assessed for 24 hr for nausea, vomiting, and complete response (no vomiting, no need for rescue antiemetics).', 'The complete response for patients with a history of motion sickness was 80.5% and 37.5% for recipients of dexamethasone and saline, respectively [P < 0.001; number needed-to-treat (NNT) = 2.3]; with corresponding incidences of 83.3% and 53.7% when there was no such history (P = 0.009; NNT = 3.4). Calculation of the efficacy of dexamethasone for the different subgroups shows that dexamethasone was 45.3% more effective in patients with motion sickness than in those without it.'] Does dexamethasone prevent postoperative nausea and vomiting more effectively in women with motion sickness?