Teeth are valued, not least for their contribution to appearance and social acceptability. The cost of treating oral disease, though, is high--about 2.2 billion pounds in the UK in 1999-2000. Nutrition and diet are major determinants of oral health or disease and the purpose of this lecture was to review their impact on the more important oral diseases: defects in the structure and appearance of teeth, dental caries, dental erosion, periodontal disease, noma, and oral cancer. There is growing realisation of the detrimental impact of dental impairment on food choice, nutrient intake and nutritional status. A common feature of many of these diseases is that the causes are well known. However, they are not yet preventable because their aetiology (and prevention) is intimately involved with lifestyle. Nevertheless, there are some hopeful signs of progress being made in several areas.