Objective: The use of complementary and alternative medicine (CAM) within the Australian community is common. The objective of this study was to determine the prevalence and pattern of CAM usage in children attending a tertiary children's hospital. Methods: We conducted a cross-sectional survey of children attending the Royal Children's Hospital, Melbourne. Children were identified by consecutive acute admissions and attendance at outpatient clinics. A structured questionnaire with items about the use of CAM in the preceding year was administered by means of a face-to-face interview. Results: Based on the 503 children surveyed, 51% reported CAM use in the preceding year. Forty-three percent had used at least one CAM medication. The most common medicinal CAM used were multivitamins, vitamin C, herbal remedies and homeopathic treatments. Non-medicinal CAM was used by 23% of the participants. The most commonly used therapies were chiropractic, naturopathy, aromatherapy, therapeutic massage and dietary restriction. The main reasons stated for CAM usage included promotion of general health and treatment of colds. Sixty-three percent of those reporting CAM use had not discussed this with their treating doctor. Conclusion: The use of CAM by children is common. Complementary and alternative medicine is particularly used for the treatment of common illnesses and conditions of childhood. Importantly, use is not always conveyed to treating physicians. Given the potential risk of adverse events associated with the use of CAM or interactions with conventional management, doctors should ask about their use as a part of routine history taking.