Aim To establish the prevalence of use of complementary and alternative medicines (CAM), including traditional Maori therapies, their perceived benefit, and frequency of adverse effects among presenters to an emergency department (ED) in New Zealand. Method An analytical cross-sectional survey of a convenience sample of patients and relatives presenting to a large tertiary ED (Waikato Hospital, Hamilton) was undertaken. Consenting participants completed a specifically designed questionnaire. Results 1043 people completed the questionnaire (participation rate 97.2%). 1 in 3 (397 or 38.1%) people had used CAM, including 29 who had used a traditional Maori therapy. CAM use was significantly more likely in females (p<0.0001), those aged 20-60yrs (p<0.001), and in those of European ethnicity (p=0.01). Only 148 (37.3%) people had told their medical practitioner that they were using CAM, and 103 (25.9%) had used conventional medicines concurrently. Most people (266, 67%) believed that CAM had been beneficial. Adverse effects were reported by 16 people (4% of users). Conclusions Many ED presenters in New Zealand use CAM. These may be associated with adverse effects, toxicity, and interactions with conventional medicines, although the incidence of these appears to be low. Doctors in New Zealand should routinely specifically enquire about the use of CAM during patient assessment.