Herbal remedies are used by many people suffering from anxiety or depression. It is therefore important to know whether they generate more good than harm. A systematic review of the published literature revealed trial data for Ginkgo biloba, Lavandula angustifolia, Hypericum perforatum, Valeriana officinalis, Crataegus oxyacantha, Eschscholzia californica, Matricaria recutita, Melissa officinalis, Passiflora incarnate and Piper methysticum. Only two of these herbal remedies are supported by sound evidence: Hypericum perforatum (St John's wort) for mild to moderate depression and Piper methysticum (kava) for anxiety. Neither is free of risks. Our knowledge of herbal remedies is incomplete and the subject merits rigorous study.