Recent decades have witnessed a significant increase in the use of complementary and alternative medicine (CAM). This includes an increased interest in, and use of, CAM in mental health, both as a primary source of treatment, and to treat side-effects of conventional medication. In the UK and elsewhere, much of CAM practice is unregulated, and the evidence base is under-developed. Many patients utilising CAMs do not disclose this to their doctors, raising risks of drug and other treatment interactions. Ethical issues associated with the use of CAM for mental health include: patient choice and consent for therapies of unknown efficacy, potential risks and benefits of CAM (including who evaluates these), and equity in terms of accessing treatments which are not generally provided as part of state-funded health services. Doctors have an ethical obligation to familiarise themselves with the range of CAM therapies their patients may be accessing and the evidence base for such treatments, both to facilitate informed decision-making on the part of their patients, and to help to minimise any potential for harm.