Awareness of risk factors for five common cancers was assessed in a representative sample of 3 693 adults in the UK. Respondents were presented with a risk of 14 factors comprising 10 which have established links with various cancers (older age, many sexual partners, low fibre diet, smoking, a relative with the cancer, low fruit and vegetable diet, taking HRT/the contraceptive pill, being overweight, viruses or infection, and a high fat diet) and four so-called "mythic" causes (food additives, overhead power lines, pollution, stress). Out of 15 well-established associations between risk factors and cancers, the average number correctly identified was 5. Women and those with higher levels of education got more correct. Endorsement of mythic causes was comparatively low (less than 5% for most cancers), but were higher in men and those with less education. These results are somewhat reassuring in relation to the prevalence of erroneous beliefs, but raise considerable concern about public understanding of well established causes. Better health education will be needed to maximise public awareness of cancer prevention.