There has been a definite increase in the popularity and use of complementary and alternative medicines, including herbal medicines, in the last ten years. The aim of this study was to determine the prevalence and patterns of use of herbal medicines and vitamin supplements by patients in the preoperative period. A questionnaire was offered to all patients attending the pre-admission clinics at St. Vincent's Hospital and Box Hill Hospital, Melbourne, over an eight-month period in 2002. In all, 1102 questionnaires were completed (91.8% response rate). The prevalence of herbal medicine use was 14.3%, with an average user age of 54.0 years and 61.4% female predominance. The five most popular herbs were Garlic, Evening Primrose, Gingko, St. John's Wort and Echinacea. The commonest reasons for herbal medicine use were acute and chronic medical conditions. 63.2% of patients had self-prescribed. 27.8% of herbal remedy users had informed the hospital doctors and 41.8% had notified their general practitioner. The prevalence of vitamin supplement use was 20.4%, with an average user age of 54.8 years and 66.2% female predominance. The five most popular vitamins were multivitamins, followed by vitamin B, C, E and D. The commonest reasons for vitamin use were maintenance of general well-being and health. The use of herbal medicines and vitamin supplements preoperatively by patients is common. Clinicians should endeavour to familiarize themselves with the more popular and significant herbal medications and, as part of the routine preoperative assessment, ask all their patients about their consumption of herbal remedies.