We have compared ondansetron 4 mg i.v. and cyclizine 50 mg i.v., in a double-blind, randomized, placebo-controlled study for the prevention of postoperative nausea and vomiting (PONV) for 24 h after day-case gynaecological laparoscopy. Compared with placebo (n = 58), ondansetron (n = 60) and cyclizine (n = 57) reduced significantly the incidence of moderate or severe nausea (30% and 23% vs 52%; P = 0.02 and P = 0.001, respectively) and requirement for escape antiemetic (28% and 16% vs 47%; P = 0.04 and P < 0.001, respectively) before discharge from hospital. There were no significant differences in PONV after discharge. Significantly more patients suffered no PONV before and after discharge after ondansetron and cyclizine compared with placebo (31% and 33% vs 12%; P = 0.02 and P < 0.01, respectively). For diagnostic laparoscopy (n = 74), fewer patients received escape antiemetic after cyclizine than after ondansetron (4% vs 37%; P < 0.01); for laparoscopic sterilization (n = 101), both antiemetics were equally effective. Ondansetron and cyclizine both reduced severe and moderate nausea and the need for antiemetic therapy after day-case gynaecological laparoscopy.