BACKGROUND: Postoperative nausea and vomiting (PONV) are still very common complications after general anesthesia. Some studies have reported that reversal of neuromuscular block by neostigmine is an important factor contributing to PONV. Whereas other studies have shown that when neostigmine is given as a reversal for muscle relaxation using mivacurium, it does not contribute to the incidence and severity of PONV. This study was designed to compare the reversible effect of neuromuscular block using neostigmine with the spontaneous recovery of neuromuscular block on the incidence and severity of PONV. METHODS: Sixty female patients undergoing laparoscopic zygote intra-fallopian transfer were studied and were allocated randomly into two groups. In Group 1 (n=30), neuromusclar block produced by mivacurium was antagonized by 1.5 mg neostigmine and 0.4 mg glycopyrrolate intravenously, whereas Group 2 (n=30) received no drugs to facilitate antagonism of blockade. The incidence and severity of PONV was assessed up to 3 hours after the operation. RESULTS: Both groups were comparable, and no differences were found in age, weight, duration of anesthesia, and the amount of mivacurium given during surgery. There were no significant differences between the two groups in the incidence and severity of PONV. CONCLUSION: This investigation has shown that when neostigmine is given as a reversal for muscle relaxation with mivacurium, it does not contribute to the incidence and severity of PONV.