Alternative medicine (AM) has become an important subject mainly because many patients and consumers use some form of AM. Despite its popularity, reliable information is rare, and misinformation of the public is a major problem. The evidence for AM is mixed, complex and heterogeneous. Some treatments are demonstrably effective for some conditions, but many are not. Despite many claims to the contrary, no form of AM is a ‘cure all’. A common assumption is that, because AM is ‘natural’, it is necessarily risk-free. However, the evidence suggests that this is not true. Most forms of AM are associated with direct risks, some of which are serious, and all AMs involve indirect risks. In conclusion, AM comprises a large range of highly diverse treatments; for most of them it is as yet unclear whether they generate more good than harm.