Summary It has been hypothesised that high iron stores increase the risk of diseases such as coronary heart disease and cancer. In summary, in spite of the theoretical possibilities that high exposure to either dietary or systemic iron might increase heart disease or cancer risk, the evidence suggests that this is not the case in healthy individuals. However, some questions remain unanswered including the risk of colon cancer in individuals with high dietary iron intakes (either via a high intake of red meat, fortified foods or frequent supplement use). It is probable that much of the non-haem iron will remain unabsorbed, which potentially may damage the colonic mucosa and increase the risk of large bowel cancer. Furthermore, the risk of cardiovascular disease and cancer in individuals who carry a mutation of HFE, the gene for haemochromatosis, many of whom may be asymptomatic, may be greater than the general population, particulary when dietary iron intake is high. This paper summarises the basis of iron metabolism and examines the theoretical reasons for an association between iron and cardiovascular disease (CVD; includes coronary disease, vascular disease & myocardial infarction) and cancer. It also revisits the studies designed to investigate the role of iron in CVD and cancer.