Dexamethasone decreases chemotherapy-induced emesis when added to an antiemetic regimen. This study was undertaken to evaluate the efficacy of granisetron/dexamethasone combination for preventing postoperative nausea and vomiting (PONV) after laparoscopic cholecystectomy (LC). In a prospective, randomized, double-blind manner, 120 patients (83 females), aged 25–65 years, were assigned to receive granisetron 40 μg kg−1 alone or granisetron 40 μg kg−1 plus dexamethasone 8 mg (n=60 of each) intravenously immediately before the induction of anaesthesia. A standardized general anaesthetic procedure and postoperative analgesia were used. A complete response, defined as no PONV and no need for another rescue antiemetic, during 0–3 h after anaesthesia was 83% with granisetron and 98% with granisetron plus dexamethasone, respectively (P=0.008); the corresponding incidence during 3–24 h after anaesthesia was 83% and 98% (P=0.008). No clinically important adverse events were observed in any of the group. In conclusion, prophylactic therapy with granisetron/dexamethasone combination is more effective than granisetron alone for the prevention of PONV after LC.