This paper describes a research study to investigate the efficacy of peppermint oil as a treatment for postoperative nausea. It uses a three-condition experimental design using statistical analysis to compare groups. The Kruskal–Wallis test was used to establish significance and the Mann–Whitney test to differentiate significance between the groups. The control, placebo and experimental groups of gynaecological patients were compared, using variables known to affect postoperative nausea. They were found to be homogeneous for the purposes of the study. A statistically significant difference was demonstrated on the day of operation, using the Kruskal-Wallis test, P= 0·0487. Using the Mann-Whitney test the difference was shown to be between the placebo and experimental group (U=3; P= 0·02). The experimental group also required less traditional antiemetics and received more opioid analgesia postoperatively. The total cost of the treatment was 48 pence per person.