We have studied the use of complimentary alternative medicine (CAM) among 233 consecutive breast cancer patients operated on at the Lund University Hospital, Sweden between 2002 and 2004. Questionnaires were administered preoperatively (n = 233), and again 3-6 months post-operatively (n = 167) and one year after surgery (n = 88). At baseline, 14,5% used CAM, 3-6 months post-operatively 14,4% used CAM and one year after surgery 18,2% used CAM. The most common products contained omega-3, garlic, ginseng and roseroot. We identified use of 35 different types of CAM products and seven of these could potentially increase the risk of breast cancer or interact with tamoxifen or aromatase inhibitors: soy, garlic, ginko biloba, echinacea, ginseng, valerian and phytoestrogens (excluding soy). Five and a half percent of the patients used either hormone replacement therapy (HRT) or hormonal contraception at the pre-operative visit, after they had received their breast cancer diagnosis. In conclusion, it is important that doctors discuss the use of CAM and exogenous hormone therapy with their breast cancer patients given the prevalence of these drugs.