Fruits and vegetables have always been a major component of the human diet in most, though not all, parts of the world. Broadly defined, fruit and vegetables are those plant foods consumed by humans, excluding cereal grains, seeds and nuts. Eating fruit and vegetables may lower the risk of cancer, particularly cancers of the gastrointestinal tract. The clearest evidence of a cancer-protective effect of eating more fruits is for stomach, oesophageal cancers. Similarly, a higher intake of vegetables probably reduces the incidence of cancer of oesophagus and colon-rectum. Fruit and vegetables contain many nutrients; they also contain other bioactive compounds that may influence many aspects of human biology and related disease processes. There is much diversity, between and within countries, both in the total amount of fruit and vegetables consumed and in the relative amounts of these two categories. Typically, consumption is highest in more affluent, better-educated, urban dwelling populations. In recent decades there has been a steady, worldwide, increasing availability of fruit and vegetables, and in year-round availability, although some regions have lagged behind.For some sites (including oesophagus and lung), despite the relatively high agreement of the study results, there are still doubts whether the results are generated by residual confounding due to smoking habits and alcohol drinking or socio-economic factors. In addition, it is not possible to rule out the possibility that recall and selection bias affects the results in the case-control studies, and confounding could be producing artefactual inverse associations in both cohort and case-control studies. However, measurement error, inadequate consideration of exposure timing and inadequate intake range may be attenuating what may be stronger inverse associations. The Working Group estimated that approximately one in ten cancers in western populations is due to an insufficient intake of fruit and vegetables. The findings of this handbook should encourage all organizations as well as governments to continue efforts to increase or maintain fruit and vegetable intake as an important objective of programs to improve nutrition to reduce the burden of cancer and other chronic diseases.