There is an increasing awareness at several levels of the need to develop pharmacovigilance practices for herbal medicines. The current model of pharmacovigilance and its associated tools have been developed in relation to synthetic drugs, and applying these methods to monitoring the safety of herbal medicines presents unique challenges in addition to those described for conventional medicines. Several problems relate to the ways in which herbal medicines are named, perceived, sourced, and utilised. Other important challenges arise from the current regulatory framework for herbal medicines in the UK. In the UK at present, the Committee on Safety of Medicines/Medicines and Healthcare products Regulatory Agency's (CSM/MHRA) 'yellow card' scheme for adverse drug reaction (ADR) reporting is the main method of monitoring the safety of herbal medicines. Despite recent initiatives to stimulate reporting of suspected ADRs associated with herbal medicines, such as extending the scheme to unlicensed herbal products, and including community pharmacists as recognised reporters, numbers of herbal ADR reports received by the CSM/MHRA remain relatively low. Under-reporting, an inevitable and important limitation of spontaneous reporting schemes, is likely to be significant for herbal medicines, since users typically do not seek professional advice about their use of such products, or report if they experience adverse effects. The herbal sector in the UK has initiated various spontaneous reporting schemes, based on the yellow card scheme, but targeted mainly at herbal-medicine practitioners. It is important that these schemes have a link with the CSM/MHRA so that potential signals are not missed. Several other tools used in pharmacovigilance of conventional medicines, such as prescription-event monitoring, and the use of computerised health-record databases, currently are of no use for evaluating the safety of herbal and other non-prescription medicines. Proposed European Union legislation for traditional herbal medicinal products will require manufacturers of products registered under new national schemes to comply with regulatory provisions on pharmacovigilance. In the longer term, other improvements in safety monitoring of herbal medicines may include modifications to existing methodology, patient reporting and greater consideration of pharmacogenetics and pharmacogenomics in optimising the safety of herbal medicines.