The use of complimentary and alternative medicines (CAM) among the UK population is on the increase. For patients requiring warfarin therapy, it is important to maintain an adequate and safe level of anticoagulation. As some forms of CAM can interact with warfarin, it is imperative that any patient considered for warfarin, is asked about their use of CAM. Our report describes the incidence and type of CAM usage among patients about to start or recently commenced on warfarin therapy attending our outpatient anticoagulant clinic. All patients attending clinic for the first time were seen by a pharmacist. A retrospective analysis of the pharmaceutical care plans for all patients seen during 2003 were analysed regarding the degree of CAM usage. Of 631 care plans reviewed, 170 (26.9%) patients were taking some form of CAM. Ninety-nine (58% of all CAM users) were taking a CAM that could interact with warfarin; the commonest forms were cod-liver oil capsules and garlic capsules. We conclude that many patients new to warfarin therapy were significant users of CAM, many of which had the potential to interact with warfarin. By taking a full drug history, potential CAM/warfarin interactions could be avoided.