Health consumers are increasingly using the Internet to access information about health care, to self-diagnose, and to purchase medication. The use of the Internet to purchase herbal products is of particular interest because of the high level of consumer expenditure on herbal medicines, and the misperception by some consumers that herbal products are natural, and thus absent of any contraindications, drug interactions and adverse effects. It is possible that consumers may purchase herbal medicines via the Internet without consulting health professionals and therefore, use these medicines in an unsafe manner. Objectives: To examine the quality of e-commerce websites that sell herbal products; specifically, websites where St. John's wort (Hypericum perforatum) can be purchased. Design: Cross-sectional survey of 54 selected websites, including online pharmacies, online health food stores and manufacturers of herbal medicines. Main outcome measure: A modified version of the DISCERN instrument was used to assess the quality of websites. Results: The majority of websites rated poorly with a concerning lack of information about the interaction between hypericum and warfarin, anti-depressants and oral contraceptives. Most sites also failed to provide sufficient information about the contraindications and adverse effects of hypericum treatment. Conclusions: The results of this study strongly support the need for improved consumer education about herbal medicine, as well as the application of more stringent standards to websites that sell medications.